What Is a Conjunction?
A conjunction is a word that connects other words, phrases, or clauses. Without conjunctions, every idea would need its own sentence, and writing would feel choppy and mechanical. Compare these two versions of the same thought:
Without conjunctions: I was tired. I finished the report. I went home.
With conjunctions: I was tired, but I finished the report before I went home.
The second version is tighter and shows how the ideas relate to each other. That is what conjunctions do: they signal relationships: addition, contrast, cause, time, condition, and more.
English has three main categories of conjunctions: coordinating, subordinating, and correlative. There is also a fourth group, conjunctive adverbs, that many people mistake for conjunctions. Each type works differently and follows its own punctuation rules.
Coordinating Conjunctions (FANBOYS)
Coordinating conjunctions join grammatically equal elements: two words, two phrases, or two independent clauses. There are exactly seven of them, and the acronym FANBOYS is the standard way to remember them.
| Letter | Conjunction | Relationship | Example |
|---|---|---|---|
| F | for | reason / cause | She stayed home, for she was feeling ill. |
| A | and | addition | He ordered coffee and a sandwich. |
| N | nor | negative addition | She didn't call, nor did she text. |
| B | but | contrast | The film was long, but it held my attention. |
| O | or | alternative | You can take the train or drive. |
| Y | yet | contrast / surprise | The price was high, yet the seats sold out. |
| S | so | result / consequence | The road was icy, so we drove slowly. |
For a deeper look at each one with additional examples, see our guide to coordinating conjunctions.
The Comma Rule for Coordinating Conjunctions
When a coordinating conjunction joins two independent clauses (meaning each side could stand alone as a complete sentence), place a comma before the conjunction.
The dog barked, and the cat bolted under the couch.
She studied for weeks, but she still felt unprepared.
When the conjunction joins only words or phrases (not two independent clauses), you do not need a comma.
He bought bread and milk. (no comma — "milk" is not an independent clause)
She was tired but happy. (no comma — "happy" is just an adjective)
Misreading this rule is one of the most common sources of comma splices and missing-comma errors. If you are unsure whether a comma belongs, ask yourself: does the material after the conjunction contain both a subject and a verb? If yes, use the comma. For a broader treatment of when commas are and are not required, the commas guide covers every major case.
Subordinating Conjunctions
Subordinating conjunctions connect an independent clause to a dependent (subordinate) clause. The dependent clause cannot stand alone as a sentence; the subordinating conjunction is what makes it subordinate, giving it a meaning that requires the main clause to be complete.
Because the flight was delayed, we missed the connection.
She called as soon as she landed.
He won't leave until you ask him to.
In each example, the subordinating conjunction introduces the dependent clause and shows how it relates to the main clause: cause and effect, time, condition, and so on.
Common Subordinating Conjunctions by Meaning
| Relationship | Subordinating Conjunctions |
|---|---|
| Time | after, as, as soon as, before, once, since, until, when, whenever, while |
| Cause / Reason | because, since, as, now that |
| Condition | if, unless, provided that, as long as, in case |
| Contrast / Concession | although, even though, though, whereas, while |
| Purpose | so that, in order that |
| Result | so that, such that |
| Comparison | as, as if, as though, than |
Notice that some words appear in more than one category. Since can express time ("I haven't seen her since Tuesday") or cause ("Since you're here, you might as well help"). While can express time ("She hummed while she worked") or contrast ("While I respect the idea, I have doubts about the execution"). Context determines meaning.
The Comma Rule for Subordinating Conjunctions
The position of the dependent clause in the sentence determines whether you need a comma.
When the dependent clause comes first, use a comma after it:
Although it was raining, we went for a walk.
Before you submit the form, check your email address.
When the dependent clause comes second, you generally do not need a comma:
We went for a walk although it was raining.
Check your email address before you submit the form.
The exception is with strongly contrastive subordinators like although, even though, and whereas, where a comma before the dependent clause can help readability even when it comes second. Both options are acceptable; the key is consistency.
Correlative Conjunctions
Correlative conjunctions always come in pairs. They work together to connect two balanced, parallel elements in a sentence. The five main pairs are:
| Pair | Example |
|---|---|
| both / and | Both the manager and the team agreed on the deadline. |
| either / or | You can either call them or send an email. |
| neither / nor | She had neither the time nor the patience for it. |
| not only / but also | He not only wrote the proposal but also presented it. |
| whether / or | I don't know whether to stay or leave. |
Parallelism with Correlative Conjunctions
The most important rule for correlative conjunctions is parallelism: the grammatical structure after the first half of the pair must match the structure after the second half. If a noun follows either, a noun must follow or. If a verb phrase follows not only, a verb phrase must follow but also.
Incorrect: She is not only talented but also she works hard.
Correct: She is not only talented but also hardworking.
Incorrect: Either you apologize or leaving is your only option.
Correct: Either you apologize or you leave.
Faulty parallelism is easy to produce and easy to miss on a quick read-through. If a sentence using correlative conjunctions feels awkward, read each half in isolation and confirm they match structurally.
Subject-Verb Agreement with Correlative Conjunctions
When correlative conjunctions join two subjects, determining which verb form to use can be tricky. The general rule is that the verb agrees with the subject closest to it.
Neither the students nor the teacher was prepared for the fire drill.
Neither the teacher nor the students were prepared for the fire drill.
This is called the proximity rule, and it applies to both either/or and neither/nor. For more on how subjects and verbs must align, the subject-verb agreement guide covers the full range of cases, including collective nouns, indefinite pronouns, and inverted sentences.
Conjunctive Adverbs: What They Are and Why They Are Not Conjunctions
Words like however, therefore, moreover, furthermore, consequently, nevertheless, and meanwhile are often called "connective words," and they do connect ideas, but they are not conjunctions. They are conjunctive adverbs, and the distinction matters because they punctuate differently.
A true conjunction can join two independent clauses with only a comma between them. A conjunctive adverb cannot. If you try to use a conjunctive adverb the same way you would use a coordinating conjunction, you create a comma splice.
Comma splice: The project ran over budget, however the client approved the extra costs.
Correct: The project ran over budget; however, the client approved the extra costs.
Also correct: The project ran over budget. However, the client approved the extra costs.
The rule: when a conjunctive adverb connects two independent clauses in a single sentence, use a semicolon before it and a comma after it. Alternatively, start a new sentence and place the conjunctive adverb at the beginning, followed by a comma. Using only a comma before a conjunctive adverb is a comma splice, one of the more persistent errors in formal writing.
| Common Conjunctive Adverbs | Relationship They Express |
|---|---|
| however, nevertheless, nonetheless, still | contrast |
| therefore, thus, consequently, as a result | result / conclusion |
| moreover, furthermore, in addition, besides | addition |
| meanwhile, subsequently, then, finally | time / sequence |
| otherwise, instead | alternative / condition |
| for example, for instance, namely | illustration |
Conjunctive adverbs are also more movable than conjunctions. You can shift them to the middle or end of a clause: "The client approved the extra costs, however." A conjunction like but or although is locked in position between the clauses it joins.
Can You Start a Sentence with a Conjunction?
Yes, and the idea that you cannot is a myth. It was never a rule of English grammar; it was a school guideline aimed at stopping young writers from stringing sentence fragments together with repeated "ands." But starting a sentence with a coordinating conjunction is perfectly standard in published writing, and has been for centuries.
And God said, Let there be light. — Genesis 1:3, King James Bible
But man is not made for defeat. — Ernest Hemingway, The Old Man and the Sea
Starting a sentence with But, And, Or, or So can create a deliberate rhetorical effect — a beat, a pivot, a punchy emphasis. The key, as with most stylistic choices, is intentionality. If the conjunction-opening sentence is a fragment rather than a complete thought, that is the problem, not the conjunction itself.
Subordinating conjunctions at the start of a sentence are equally fine: "Because the bridge was under repair, we took the longer route." This is simply a sentence where the dependent clause comes first, which requires a comma after it. There is nothing grammatically problematic about it.
Common Mistakes with Conjunctions
1. Comma Splice with a Conjunctive Adverb
Incorrect: I studied all night, therefore I passed the exam.
Correct: I studied all night; therefore, I passed the exam.
Remember: therefore is not a conjunction. It cannot join two independent clauses with only a comma.
2. Missing Comma Before a Coordinating Conjunction
Incorrect: She finished the draft and she sent it to her editor.
Correct: She finished the draft, and she sent it to her editor.
Both sides of and here are independent clauses ("She finished the draft" and "she sent it to her editor"), so a comma is required before the conjunction.
3. Broken Parallelism in Correlative Pairs
Incorrect: He wants not only a promotion but also to be given more flexibility.
Correct: He wants not only a promotion but also more flexibility.
After not only we have a noun phrase ("a promotion"), so after but also we also need a noun phrase ("more flexibility"), not a verb phrase ("to be given more flexibility").
4. "Neither/Nor" and "Either/Or" Confusion
Incorrect: Neither the report or the presentation was ready.
Correct: Neither the report nor the presentation was ready.
Neither always pairs with nor. Either always pairs with or. Mixing them ("neither...or," "either...nor") is a consistent error that proofreading tools and a careful grammar checker will catch.
5. Using "But" and "Although" Together
Incorrect: Although she was tired, but she kept working.
Correct: Although she was tired, she kept working.
Also correct: She was tired, but she kept working.
Although and but both express contrast. Using them together in the same clause is redundant and grammatically wrong: they compete for the same connective job. Choose one or the other.
6. "While" and "Since" Used Ambiguously
Both words carry two distinct meanings, and careless use can produce sentences that are technically readable in two different ways.
While she was in the meeting, the decision was made. (time? contrast?)
Since he joined the team, results have improved. (time? cause?)
In most contexts, readers can work out the intended meaning from context. But if there is any chance of ambiguity, substitute a more precise word. Use whereas or although for contrast; use because or now that for cause; use ever since or after for time.
Quick Reference: The Three Types at a Glance
| Type | Examples | What They Join | Comma Rule |
|---|---|---|---|
| Coordinating | for, and, nor, but, or, yet, so | Equal elements (words, phrases, or independent clauses) | Comma before the conjunction when joining two independent clauses |
| Subordinating | because, although, if, when, since, unless, until, while… | A dependent clause to an independent clause | Comma after the dependent clause when it comes first; usually no comma when it comes second |
| Correlative | both/and, either/or, neither/nor, not only/but also, whether/or | Parallel elements in pairs | No comma between the pair elements unless each is a full independent clause |
Frequently Asked Questions About Conjunctions
What is the difference between a coordinating and a subordinating conjunction?
A coordinating conjunction joins elements of equal grammatical rank: two nouns, two phrases, or two independent clauses. A subordinating conjunction introduces a dependent clause that cannot stand alone without the main clause. A sentence joined by but or and can be split into two independent sentences; a clause introduced by because or although cannot.
Is "however" a conjunction?
No. However is a conjunctive adverb. It connects ideas and can appear within a clause, but it cannot join two independent clauses with only a comma between them. Writing "I was tired, however, I kept going" is a comma splice. The correct construction uses a semicolon: "I was tired; however, I kept going." See the commas guide for more on punctuating these words.
When do you put a comma before "and"?
Put a comma before and when it joins two independent clauses: "She studied all morning, and she still had questions." Do not use a comma when and joins only two words or phrases: "bread and butter," "tired and hungry." In a list of three or more items, the comma before the final and (the Oxford comma) is optional but recommended for clarity.
Can "because" start a sentence?
Yes. "Because she practiced every day, her performance improved noticeably." The dependent clause comes first, followed by a comma, and then the main clause. This is standard English. The caution is against writing a sentence that is only the because-clause with no main clause to complete it. That produces a fragment, not an incorrect conjunction use.
What is the FANBOYS acronym?
FANBOYS stands for the seven coordinating conjunctions: For, And, Nor, But, Or, Yet, So. It is a memory device used in grammar instruction to help writers remember all seven. Because there are exactly seven coordinating conjunctions in English, the acronym is complete: if a word is not in FANBOYS, it is not a coordinating conjunction.
What is the difference between "although" and "but"?
Although is a subordinating conjunction; but is a coordinating conjunction. Both express contrast, but they attach differently. But joins two independent clauses of equal weight: "She was tired, but she kept working." Although introduces a dependent clause: "Although she was tired, she kept working." The meaning is nearly identical; the grammatical structure is different. You cannot combine them in the same clause: "Although she was tired, but she kept working" is incorrect.