Connect independent clauses with coordinating conjunctions. Create balanced compound structures.
约8分钟阅读
A compound sentence joins two or more independent clauses -- clauses that could each stand alone as complete sentences. The most common way to build a compound sentence is with a coordinating conjunction.
English has exactly seven coordinating conjunctions. The acronym FANBOYS makes them easy to remember:
| Letter | Conjunction | Core Meaning |
|---|---|---|
| F | for | gives a reason (because) |
| A | and | adds information |
| N | nor | adds a negative alternative |
| B | but | shows contrast |
| O | or | offers an alternative |
| Y | yet | shows contrast despite expectation |
| S | so | shows a result |
Every compound sentence built with a coordinating conjunction follows one structure:
Independent clause + comma + coordinating conjunction + independent clause.
Each independent clause has its own subject and verb and expresses a complete thought.
The rain stopped**,** and the sun came out.
Subject 1 + Verb 1 ... , conjunction ... Subject 2 + Verb 2
Notice three things:
For explains why the first clause is true. It works like "because," but it sounds more formal and always introduces a clause (not just a phrase).
She stayed home**, for** she was feeling ill.
The park was empty**, for** a storm was approaching.
He accepted the offer**, for** it was too good to refuse.
Usage notes:
And is the most frequently used coordinating conjunction. It connects ideas that are similar, equal, or that happen together.
The students finished the exam**, and** the teacher collected the papers.
She writes novels**, and** her brother writes screenplays.
I opened the door**, and** the cat ran inside.
Common uses of and:
| Function | Example |
|---|---|
| Addition | He bought groceries**, and** she cooked dinner. |
| Sequence | She pressed the button**, and** the machine started. |
| Simultaneous actions | The children laughed**, and** the dog barked. |
| Cause and effect (informal) | He studied hard**, and** he passed the exam. |
Warning: And is the most overused conjunction in student writing. If you find yourself chaining several clauses with and, consider whether a different conjunction or sentence structure would be clearer. We address this in Section 3.
Nor connects two negative ideas. It means "and also not." After nor, the subject and auxiliary verb invert (switch positions), just like in a question.
She did not call**, nor** did she send a message.
The manager was not available**, nor** was his assistant.
He does not eat meat**, nor** does he eat dairy.
Structure after nor:
... , nor + auxiliary verb + subject + main verb
| First clause (negative) | Second clause with nor |
|---|---|
| He cannot swim | , nor can he ride a bicycle. |
| They have not replied | , nor have they acknowledged the email. |
| I will not attend | , nor will I send a representative. |
Tip: Nor is relatively rare in casual writing but valuable in formal essays and academic writing. It adds variety and precision when you need to present multiple negative ideas.
But signals that the second clause contradicts, limits, or contrasts with the first.
The test was difficult**, but** most students passed.
I wanted to help**, but** I did not know how.
She is young**, but** she has remarkable experience.
When to use but:
The evidence seems strong**, but** several experts have raised doubts.
Or presents a choice, an alternative, or a possibility.
You can take the bus**, or** you can walk.
We should leave now**, or** we will miss the flight.
She can apply for the scholarship**, or** she can take out a loan.
Common uses of or:
| Function | Example |
|---|---|
| Choice between options | You can stay**, or** you can go. |
| Consequence / warning | Hurry up**, or** you will be late. |
| Restating in other words | The study was inconclusive**, or** in other words, it proved nothing. |
Yet is similar to but, with an added sense of surprise or something happening despite what you would expect.
He trained every day**, yet** he did not win the race.
The instructions were clear**, yet** many participants made errors.
She had little formal education**, yet** she became one of the most respected scientists in her field.
But vs. Yet:
The weather was terrible**, but** we stayed inside. (simple contrast)
The weather was terrible**, yet** the hikers continued up the mountain. (unexpected contrast)
So indicates that the second clause is a result or consequence of the first.
The library was closed**, so** I studied at home.
She missed the deadline**, so** her application was rejected.
The evidence was overwhelming**, so** the jury reached a quick verdict.
When to use so:
The data supports the hypothesis**, so** we can proceed to the next phase.
When a coordinating conjunction joins two independent clauses, place a comma before the conjunction.
✓ The experiment failed**, and** the team redesigned the procedure.
✗ The experiment failed and the team redesigned the procedure.
Exception: When the two independent clauses are both very short (typically five words or fewer each), some style guides allow omitting the comma.
She sang and he played. (Acceptable without comma because both clauses are very short.)
However, in academic and formal writing, it is safest to always include the comma. You will never be marked wrong for including it, but you may be marked wrong for leaving it out.
A compound predicate is when one subject has two verbs joined by a conjunction. This is NOT a compound sentence and does NOT need a comma.
She opened the book and started reading. (One subject, two verbs -- no comma.)
He ran to the store but forgot his wallet. (One subject, two verbs -- no comma.)
Compare with a compound sentence:
She opened the book**, and** her brother turned on the television. (Two subjects, two verbs -- comma required.)
The test is simple: Does the clause after the conjunction have its own subject? If yes, it is a compound sentence, and you need a comma. If the subject is shared, it is a compound predicate, and you do not.
| Conjunction | Meaning | Example |
|---|---|---|
| for | reason | He left early**, for** he had a meeting. |
| and | addition | She smiled**, and** he waved. |
| nor | negative addition | He won't go**, nor will** he explain why. |
| but | contrast | I agree**, but** I have concerns. |
| or | alternative | Call me**, or** send an email. |
| yet | unexpected contrast | It rained**, yet** we enjoyed the trip. |
| so | result | The road was blocked**, so** we turned around. |
Remember: Independent clause + comma + FANBOYS conjunction + independent clause.
约7分钟阅读
Coordinating conjunctions are the most common way to join independent clauses, but they are not the only way. This section covers all three punctuation methods for compound sentences and explains when to use each one.
This is the method covered in Section 1. It is the most common and most versatile approach.
Independent clause , conjunction independent clause.
The proposal was well researched**, and** the committee approved it unanimously.
He wanted to participate**, but** his schedule did not allow it.
When to use this method:
A semicolon can join two independent clauses without a conjunction. The semicolon signals that the two ideas are closely related.
Independent clause ; independent clause.
The experiment produced unexpected results**;** the team decided to repeat it.
Some students prefer lectures**;** others learn better through discussion.
The deadline is Friday**;** no extensions will be granted.
Both sides must be independent clauses. Each side must have a subject and verb and express a complete thought.
✓ The road was icy**;** several cars skidded off the highway.
✗ The road was icy**;** causing several accidents. ("Causing several accidents" is not an independent clause.)
The two clauses must be closely related in meaning. A semicolon tells the reader: "These ideas belong together." If the two clauses are about unrelated topics, use a period instead.
✓ She speaks three languages**;** her job requires frequent travel abroad. (Related: languages and international work.)
✗ She speaks three languages**;** the weather was pleasant. (Unrelated ideas -- use a period.)
Do not capitalize the word after the semicolon (unless it is a proper noun).
✓ The results were clear**;** further testing was unnecessary.
✗ The results were clear**;** Further testing was unnecessary.
| Use a semicolon when... | Example |
|---|---|
| The relationship is obvious without a conjunction | She studied all night**;** she passed the exam. |
| You want a crisper, more sophisticated rhythm | The data supports the claim**;** the conclusion is sound. |
| You want to create a parallel or balanced feel | Some lead**;** others follow. |
| The clauses are short and punchy | He lied**;** she knew. |
Tip: Think of a semicolon as a "soft period." It creates a longer pause than a comma but a shorter one than a period. It is especially useful in academic and formal writing where you want to show a tight logical connection between two ideas.
A conjunctive adverb is a transitional word that shows the relationship between two independent clauses. Common conjunctive adverbs include:
| Category | Conjunctive Adverbs |
|---|---|
| Addition | furthermore, moreover, additionally, also, besides |
| Contrast | however, nevertheless, nonetheless, conversely, instead, on the other hand |
| Result | therefore, consequently, accordingly, thus, hence, as a result |
| Time | meanwhile, subsequently, afterward, then, finally |
| Emphasis | indeed, in fact, certainly |
| Example | for example, for instance, specifically, namely |
| Summary | in summary, in conclusion, overall |
Independent clause ; conjunctive adverb , independent clause.
Notice the pattern carefully: semicolon before the conjunctive adverb, comma after it.
The data was incomplete**; therefore,** the researchers collected additional samples.
She had extensive qualifications**; however,** the company chose another candidate.
The first experiment failed**; consequently,** the team revised their methodology.
Enrollment increased by 20%; meanwhile, funding was cut by 15%.
This is one of the most common punctuation errors in academic writing. Students often put only a comma before a conjunctive adverb, which creates a comma splice (a type of run-on sentence).
| Wrong (comma splice) | Correct |
|---|---|
| The plan seemed effective**,** however**,** it failed. | The plan seemed effective**; however,** it failed. |
| She studied hard**,** therefore**,** she passed. | She studied hard**; therefore,** she passed. |
| The budget was tight**,** consequently**,** we cut costs. | The budget was tight**; consequently,** we cut costs. |
Why this matters: Conjunctive adverbs like however, therefore, and meanwhile are not strong enough to join independent clauses on their own. They need a semicolon (or a period) before them. Only the seven FANBOYS conjunctions can join independent clauses with just a comma.
Conjunctive adverbs can appear in different positions within the second clause. No matter where they appear, the semicolon goes between the two clauses.
Beginning of the second clause (most common):
The deadline passed**; however,** she submitted the report anyway.
Middle of the second clause:
The deadline passed**;** she submitted the report**, however,** anyway.
End of the second clause:
The deadline passed**;** she submitted the report anyway**, however.**
When the conjunctive adverb moves to the middle or end, it is set off by commas on both sides (or a comma before it at the end).
Here is the same idea expressed using each method:
Comma + conjunction:
The survey results were surprising**, and** the researchers wanted to investigate further.
Semicolon alone:
The survey results were surprising**;** the researchers wanted to investigate further.
Semicolon + conjunctive adverb:
The survey results were surprising**; consequently,** the researchers wanted to investigate further.
All three are grammatically correct. The choice depends on the tone and emphasis you want:
| Method | Tone | Best for |
|---|---|---|
| Comma + conjunction | Conversational, smooth | General writing, storytelling |
| Semicolon alone | Crisp, sophisticated | Balanced or parallel ideas |
| Semicolon + conjunctive adverb | Formal, explicit | Academic writing, complex arguments |
Using only a comma between two independent clauses without a coordinating conjunction.
✗ The project is due Monday**,** we need to start now.
✓ The project is due Monday**, so** we need to start now.
✓ The project is due Monday**;** we need to start now.
Do not use a semicolon before a FANBOYS conjunction (in most cases). Use a comma.
✗ The budget was approved**;** but the timeline was extended.
✓ The budget was approved**, but** the timeline was extended.
Exception: When the independent clauses themselves contain commas, you may use a semicolon before the conjunction for clarity.
The committee included Dr. Smith, the chair**;** Professor Lee, the secretary**;** and Ms. Brown, the treasurer.
We visited Paris, France**;** Rome, Italy**;** and Berlin, Germany.
This use of the semicolon as a "super comma" in lists with internal commas is a separate rule from compound sentences.
Do not use a semicolon before words like because, although, when, if, or while. These introduce dependent clauses, not independent ones.
✗ She succeeded**;** because she worked hard.
✓ She succeeded because she worked hard.
| Pattern | Example |
|---|---|
| clause , FANBOYS clause | I called**, but** no one answered. |
| clause ; clause | I called**;** no one answered. |
| clause ; adverb , clause | I called**; however,** no one answered. |
| clause . Clause. | I called**.** No one answered. |
All four patterns correctly separate two independent clauses. The first three create compound sentences. The fourth creates two simple sentences.
When editing your writing, look at every comma that falls between what might be two independent clauses. Ask: "Is there a FANBOYS conjunction after this comma?" If not, you may have a comma splice. Replace the comma with a semicolon, add a conjunction, or use a period.
Self-check: Cover everything after the comma. Does what remains before the comma form a complete sentence? Now cover everything before the comma (including the conjunction, if any). Does what remains form a complete sentence? If both answers are yes, make sure you have used the correct punctuation pattern.
约8分钟阅读
Knowing the rules for compound sentences is only the beginning. Writing them well requires attention to balance, variety, and emphasis. This section shows you how to move from grammatically correct compound sentences to compound sentences that are clear, engaging, and purposeful.
A balanced compound sentence gives roughly equal weight to both clauses. When both clauses are similar in length and importance, the sentence feels natural and easy to read.
Balanced: The research confirmed the hypothesis**, and** the team published their findings.
Unbalanced: The research, which had been conducted over a period of three years across multiple institutions using a variety of advanced statistical methods, confirmed the hypothesis**, and** they published it.
In the unbalanced version, the first clause is so long and dense that the second clause feels like an afterthought. The reader has to hold too much information in mind before reaching the conjunction.
When two ideas are equally important, keep the clauses at roughly similar lengths. You do not need to count words exactly, but the clauses should feel proportional.
The economy grew steadily**, but** unemployment remained high.
She presented the data**, and** the audience asked thoughtful questions.
The first trial failed**, so** the researchers adjusted their approach.
Each clause is roughly the same length. Neither overwhelms the other.
If one clause is significantly longer than the other, consider one of these fixes:
Option A: Shorten the long clause.
✗ The city, which had been experiencing rapid population growth for the past decade due to economic opportunities in the technology sector, invested in new infrastructure**, and** traffic improved.
✓ The rapidly growing city invested in new infrastructure**, and** traffic improved.
Option B: Expand the short clause.
✗ The proposal addressed funding, staffing, scheduling, community outreach, and long-term sustainability**, and** the board liked it.
✓ The proposal addressed funding, staffing, scheduling, community outreach, and long-term sustainability**, and** the board voted unanimously to approve it.
Option C: Split into two sentences.
✗ After years of careful research involving dozens of scientists from institutions around the world, the team finally identified the gene responsible for the condition**, and** they published a paper.
✓ After years of careful research involving dozens of scientists from institutions around the world, the team finally identified the gene responsible for the condition. They published their findings in a leading journal.
Guideline: If one clause is more than twice the length of the other, the sentence will probably feel unbalanced. Restructure it.
Balance is not just about length -- it is about how important each idea is. A compound sentence implies that both clauses are equally significant. If one idea is clearly more important than the other, a compound sentence may not be the best structure.
The government raised taxes**, and** public spending increased.
She won the award**, but** she remained humble.
Both ideas carry similar weight. They deserve equal grammatical status.
If one idea is the main point and the other is supporting detail, a complex sentence (with a subordinate clause) may work better.
Compound (equal weight): The storm knocked out the power**, and** the school canceled classes.
Complex (main idea emphasized): Because the storm knocked out the power**, the school canceled classes.** (The cancellation is the main point; the storm is the reason.)
Compound (equal weight): She studied for months**, and** she passed the bar exam.
Complex (main idea emphasized): After studying for months**, she passed the bar exam.** (Passing the exam is the main point.)
Tip: If you can turn one clause into a because, although, when, after, or while clause without losing meaning, the ideas may not be truly equal -- and a complex sentence might serve you better.
The conjunction and is the default connector in most people's writing. Overusing it creates a flat, monotonous rhythm that makes your writing sound immature.
✗ I woke up early**, and** I ate breakfast**, and** I drove to work**, and** I attended a meeting**, and** I finished my report.
This sentence strings five clauses together with and. Every clause gets equal weight, so nothing stands out. The writing feels like a list of events rather than a narrative with purpose.
Strategy 1: Use different conjunctions.
I woke up early and ate breakfast. I drove to work**, but** traffic made me late**, so** I missed the first part of the meeting.
Strategy 2: Use subordination to vary structure.
After waking up early and eating breakfast, I drove to work. Although I arrived on time, I missed the first part of the meeting because the room had changed.
Strategy 3: Use semicolons or conjunctive adverbs.
I woke up early and ate breakfast**;** I then drove to work. The meeting, however, started before I arrived.
Strategy 4: Use short simple sentences for variety.
I woke up early. After breakfast, I drove to work and arrived just in time for the meeting.
Here is a paragraph that uses several different FANBOYS conjunctions along with other structures:
The committee reviewed the proposal carefully**, but** several members raised concerns about the budget. The chair acknowledged these issues**, so** she formed a subcommittee to revise the financial projections. The original timeline was tight**, yet** the team remained confident they could meet the deadline. They could either reduce the scope of the project**, or** they could request additional funding from the dean.
Notice how each conjunction adds a different logical relationship: contrast, result, unexpected confidence, and alternatives. The writing feels dynamic because the connections between ideas vary.
Compound sentences are not just neutral connectors. The structure itself can create emphasis, contrast, and rhythm when used thoughtfully.
The but and yet conjunctions naturally create emphasis on the second clause. Readers pay more attention to what comes after the contrast.
The evidence seemed overwhelming**, but** the jury voted to acquit.
The task looked simple**, yet** it took three months to complete.
Whatever follows but or yet is the idea the reader will remember. Place your most important point there.
A short second clause after a longer first clause creates a punchy, memorable ending.
The team spent six months developing the product, testing it across multiple markets, and gathering user feedback**, but** nobody bought it.
He had the best grades in his class, the strongest recommendations, and years of relevant experience**, yet** he did not get the job.
The short final clause lands with force precisely because it contrasts with the length of what came before.
When both clauses use parallel grammatical structures, the sentence gains a rhythmic, memorable quality.
Parallel: The rich get richer**, and** the poor get poorer.
Parallel: She came**, she saw**, she conquered. (Note: this famous example uses commas without conjunctions for dramatic effect -- a deliberate rhetorical choice called asyndeton.)
Parallel: Some people dream of success**, while** others wake up and work for it.
Parallel: Ask not what your country can do for you**;** ask what you can do for your country.
Parallel structure makes compound sentences feel polished and intentional. It is especially effective in persuasive writing, speeches, and conclusions.
Not every pair of related ideas should become a compound sentence. Here are situations where other structures work better:
| Situation | Better Structure | Example |
|---|---|---|
| One idea depends on the other | Complex sentence | Because it rained, the game was canceled. |
| You want to emphasize one idea | Simple sentence + detail | The project failed. Budget cuts were the primary cause. |
| Three or more ideas in sequence | List or varied sentences | First, we gathered data. Then, we analyzed it. Finally, we wrote the report. |
| The connection is obvious | Two simple sentences | It started to rain. We went inside. |
Here are three examples showing how unbalanced compound sentences can be improved.
Example 1:
Before: The survey, which was distributed to over 5,000 participants across twelve countries and took approximately six months to complete and analyze, revealed significant cultural differences in communication preferences**, and** this was interesting.
After: The international survey revealed significant cultural differences in communication preferences**, and** the researchers plan to publish their full analysis next month.
Example 2:
Before: He ran**, and** he went to the store**, and** he bought milk**, and** he came home**, and** he made dinner.
After: He ran to the store and bought milk. When he got home, he made dinner.
Example 3:
Before: The new policy reduced costs**, and** it was implemented last year.
After: The new policy, implemented last year, reduced costs. (The timing is a minor detail, so it works better as a modifying phrase rather than an equal clause.)
| Principle | Guideline |
|---|---|
| Match clause length | Keep clauses proportional; split if one is much longer |
| Match clause importance | Equal ideas = compound; unequal ideas = complex sentence |
| Avoid and-chains | Vary conjunctions; mix simple, compound, and complex sentences |
| Use emphasis strategically | Place your key point after but/yet; use short second clauses for punch |
| Use parallelism | Mirror grammatical structure for rhythm and polish |
| Know when to stop | Not every pair of ideas needs a conjunction |
约8分钟阅读
A run-on sentence occurs when two or more independent clauses are joined incorrectly -- either with no punctuation at all or with only a comma (and no conjunction). Run-on sentences are among the most common and most penalized errors in academic writing.
This section explains the two types of run-ons, shows you how to identify them, and gives you a clear reference chart for fixing each type.
An independent clause has a subject, a verb, and expresses a complete thought. When you have two independent clauses, you must connect them properly. If you do not, you have a run-on.
There are two types of run-on sentences:
| Type | What It Looks Like | Example |
|---|---|---|
| Fused sentence | Two clauses with NO punctuation between them | The report is due Friday we need to finish it today. |
| Comma splice | Two clauses joined with ONLY a comma (no conjunction) | The report is due Friday, we need to finish it today. |
Both are errors. Both need to be fixed.
A fused sentence (also called a run-on in the strict sense) occurs when two independent clauses are written one after another with no punctuation or conjunction between them.
✗ The experiment was successful the team celebrated.
✗ She completed the assignment on time he submitted his late.
✗ Climate change is a global challenge every country must contribute to the solution.
✗ The library closes at nine we should leave soon.
Read your sentence aloud. If you naturally pause in the middle and the parts on either side of the pause could each be a complete sentence, check whether you have punctuation at that pause point. If there is nothing there, you have a fused sentence.
Test it:
"The experiment was successful" -- Complete sentence? Yes.
"The team celebrated" -- Complete sentence? Yes.
Punctuation between them? No. --> This is a fused sentence.
A comma splice occurs when two independent clauses are joined with only a comma -- no coordinating conjunction follows the comma.
✗ The results were inconclusive**,** more testing is needed.
✗ She is an excellent writer**,** her essays always receive high marks.
✗ The budget was approved**,** the project can move forward.
✗ I enjoy reading**,** my sister prefers watching films.
Comma splices are more common than fused sentences because writers sense that a connection is needed between the clauses and instinctively add a comma. The comma is the right instinct -- but it is not strong enough on its own to join two independent clauses.
Remember: A comma can join independent clauses only when it is followed by one of the seven coordinating conjunctions (for, and, nor, but, or, yet, so).
Comma splices are especially common before conjunctive adverbs like however, therefore, furthermore, meanwhile, consequently, and nevertheless. These words look like conjunctions but are not coordinating conjunctions.
✗ The plan seemed effective**,** however**,** it failed in practice.
✗ Costs increased significantly**,** therefore**,** the company reduced staff.
✗ The first trial produced no results**,** consequently**,** the team tried a different approach.
Fix: Use a semicolon before the conjunctive adverb.
✓ The plan seemed effective**; however,** it failed in practice.
✓ Costs increased significantly**; therefore,** the company reduced staff.
Every run-on sentence -- whether fused or comma splice -- can be fixed using one of these four methods.
The simplest fix. Separate the clauses into two independent sentences.
Fused: The data supports the conclusion the research is complete.
Fixed: The data supports the conclusion**.** The research is complete.
Comma splice: She finished the project early**,** she submitted it ahead of the deadline.
Fixed: She finished the project early**.** She submitted it ahead of the deadline.
When to use this fix: When the ideas are related but do not need to be in the same sentence, or when you want short, direct sentences for emphasis.
Join the clauses with a comma followed by one of the FANBOYS conjunctions.
Fused: The weather was perfect the game was canceled.
Fixed: The weather was perfect**, but** the game was canceled.
Comma splice: He studied all week**,** he felt confident about the exam.
Fixed: He studied all week**, so** he felt confident about the exam.
When to use this fix: When you want to show a clear logical relationship (contrast, result, addition, etc.) between the clauses.
Join the clauses with a semicolon, with or without a conjunctive adverb.
Fused: The proposal was rejected the team revised it immediately.
Fixed: The proposal was rejected**;** the team revised it immediately.
Fixed: The proposal was rejected**; consequently,** the team revised it immediately.
Comma splice: The evidence was strong**,** the jury still deliberated for hours.
Fixed: The evidence was strong**;** the jury still deliberated for hours.
Fixed: The evidence was strong**; nevertheless,** the jury deliberated for hours.
When to use this fix: When the clauses are closely related and you want a tighter connection than two separate sentences provide, especially in formal or academic writing.
Turn one of the independent clauses into a dependent clause by adding a subordinating word (because, although, when, while, if, after, before, since, unless, etc.).
Fused: The factory closed hundreds of workers lost their jobs.
Fixed: When the factory closed**,** hundreds of workers lost their jobs.
Fixed: Hundreds of workers lost their jobs because the factory closed.
Comma splice: She was the most qualified candidate**,** she did not get the position.
Fixed: Although she was the most qualified candidate**,** she did not get the position.
When to use this fix: When one idea is more important than the other, or when one idea is a cause, condition, or time frame for the other.
| What You Wrote | Problem | Fix Options |
|---|---|---|
| Clause 1 Clause 2 (no punctuation) | Fused sentence | 1. Clause 1**.** Clause 2. |
| 2. Clause 1**, conjunction** Clause 2. | ||
| 3. Clause 1**;** Clause 2. | ||
| 4. Subordinator Clause 1**,** Clause 2. | ||
| Clause 1**,** Clause 2 (comma only) | Comma splice | 1. Clause 1**.** Clause 2. |
| 2. Clause 1**, conjunction** Clause 2. | ||
| 3. Clause 1**;** Clause 2. | ||
| 4. Subordinator Clause 1**,** Clause 2. | ||
| Clause 1**,** however**,** Clause 2 | Comma splice (with conjunctive adverb) | 1. Clause 1**. However,** Clause 2. |
| 2. Clause 1**; however,** Clause 2. |
Use this three-step editing process to catch run-on sentences:
Read each sentence and identify every finite verb (a verb with a subject that shows tense). If a sentence has two or more finite verbs, it might contain two independent clauses.
"The report was thorough it covered all the key issues."
Verb 1: "was" (subject: report) -- Verb 2: "covered" (subject: it)
Two finite verbs, two subjects --> possible run-on.
Identify where one clause ends and the next begins. Usually, the boundary is where a new subject appears.
"The report was thorough | it covered all the key issues."
The boundary is between "thorough" and "it."
Ask: What punctuation (if any) appears at the boundary?
| What Is There | Status |
|---|---|
| Nothing | Fused sentence -- fix it |
| Comma only | Comma splice -- fix it |
| Comma + FANBOYS conjunction | Correct compound sentence |
| Semicolon | Correct compound sentence |
| Semicolon + conjunctive adverb + comma | Correct compound sentence |
| Period | Correct (two separate sentences) |
In creative and informal writing, very short parallel clauses are sometimes joined with commas without conjunctions for rhythmic effect:
I came, I saw, I conquered.
He ran, she followed, they disappeared.
This is a deliberate stylistic choice called asyndeton. It is acceptable in creative writing and speeches but should be avoided in formal academic essays.
Starting a sentence with and or but is not a run-on sentence. It is a stylistic choice that is widely accepted in modern writing.
The committee reviewed the proposal. But they decided to delay the vote.
This is grammatically correct. "But they decided to delay the vote" is one independent clause that begins with a conjunction for emphasis. Some traditional style guides discourage this practice, but most modern guides accept it.
A long sentence is not automatically a run-on. A sentence can be long and still be grammatically correct if it uses conjunctions and punctuation properly.
Although the initial results were discouraging, the team continued their research, and after three more months of testing, they discovered a pattern that none of the previous studies had identified, which ultimately led to a breakthrough in the treatment of the disease.
This sentence is long (46 words), but every clause is properly connected. It is not a run-on. However, it might benefit from being broken into shorter sentences for clarity.
Certain sentence patterns frequently produce run-ons. Be especially careful with these:
| Pattern | Run-on Example | Corrected |
|---|---|---|
| Pronoun subjects (it, he, she, they, this, that) | The company expanded**,** it hired 200 people. | The company expanded**, and** it hired 200 people. |
| Transitional words (then, also, next) | She finished the draft**,** then she proofread it. | She finished the draft**;** then**,** she proofread it. |
| Explanations | The test was hard**,** most students failed. | The test was hard**;** most students failed. |
| Conjunctive adverbs | Sales dropped**,** therefore**,** we cut the budget. | Sales dropped**; therefore,** we cut the budget. |
| Cause and effect | It rained all day the match was postponed. | It rained all day**, so** the match was postponed. |
Use this checklist every time you revise an essay:
Read each sentence and count the independent clauses. If there are two or more, check the connection.
Look at every comma. Is there a FANBOYS conjunction after it? If not, check whether both sides are independent clauses. If they are, you have a comma splice.
Search for conjunctive adverbs (however, therefore, meanwhile, furthermore, consequently, nevertheless). Is there a semicolon or period before each one? If only a comma, fix it.
Read long sentences aloud. If you run out of breath or lose track of the main idea, the sentence may need to be split.
Check sentences that start with pronouns (it, he, she, they, this, that). These are often the second clause of a run-on that was not punctuated correctly.
| Concept | Key Point |
|---|---|
| Fused sentence | Two clauses, no punctuation between them |
| Comma splice | Two clauses joined by only a comma |
| Fix 1 | Period -- make two sentences |
| Fix 2 | Comma + FANBOYS conjunction |
| Fix 3 | Semicolon (with or without conjunctive adverb) |
| Fix 4 | Subordinate one clause (because, although, when, etc.) |
| Most common trap | Comma before however, therefore, consequently |
| Editing strategy | Find the verbs, find the boundary, check the punctuation |
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