When should I place a comma in front of "and" or "but"?

Question

This is a common question that will be addressed below.

Answer 1

"And" and "but" are considered coordinating conjunctions or coordinators. They are conjunctions that -coordinate- two or more items: words, phrases, and sentences. An acronym to remember coordinating conjunctions is called FANBOYS, which represent coordinating conjunctions for, and, nor, but, or, yet, and so. You would place a comma in front of any coordinating conjunction if the two clauses are independent clauses (they can stand alone as a sentence).

For example:

I went to the store to buy bread, and I stopped by the dairy section to grab some milk.

"I went to the store to buy bread," is a complete sentence as well as "I stopped by the dairy section to grab some milk." Because the coordinating conjunction is between two independent clauses, you use a comma. The coordinator is not strong enough to stand alone.

You do not have to use a comma if the coordinator is between an independent clause and dependent clause.

For example:

I went to the store and bought bread.

Bought bread cannot stand alone as a complete sentence; therefore, a comma does not need to be used in front of the coordinating conjunction.

Answer 2

Placing a comma before "and" or "but" often depends on the structure of the sentence and the relationship between the clauses. Here are some general guidelines:

1. Independent Clauses (Compound Sentences):
2. Use a comma before "and" or "but" when joining two independent clauses (complete sentences) to form a compound sentence. Example: "She wanted to go to the park, but it started raining."
3. Coordinating Conjunction in a Series:
4. When listing items in a series (three or more items), a comma before "and" (called the Oxford comma) can clarify the list's elements. Example: "He bought apples, oranges, and bananas."
5. No Comma in Single Compound Predicate:
6. If the "and" or "but" is joining parts of a single compound predicate (one subject with multiple verbs or objects), no comma is needed. Example: "She baked a cake and decorated it beautifully."
7. Adjectives or Adverbs:
8. Generally, no comma is needed before "and" or "but" when joining adjectives or adverbs. Example: "It was a long and tiring journey."
9. Subordinate Clauses:
10. If "and" or "but" joins a subordinate clause to the main clause, no comma is used unless there are specific reasons for punctuation based on sentence structure or style. Example: "He ate quickly so that he could finish early and relax."

Answer 3

Both answers above are accurate and helpful. To put it simply: Use a comma before a conjunction that is combining two clauses so the reader is able to understand. If the sentence is short, you do not need a comma. For example:

I went to the store and I stopped for gas.

Stella and Jacob were snappily skipping along on their way to the store, but they forgot their money!

Answer 4

What James wrote is all great. I'd just like to add a little about when to use commas when listing nouns. Please look at the following examples.

I like apples, pears, and oranges. Here you need to put a comma before "and" because it is the last item in the list of three items.

Another example would be: My favorite sports are soccer, tennis, skiing, and snowboarding. If there are three or more things listed, a comma goes before the "and."

I like strawberries and bananas. You don't need a comma before "and" in this case because there are only two items.