If the number of page visits is a reliable indicator, this topic—using a comma before and—is on the minds of many people. The third most oft-visited on this site, this page garnered close to 10,000 hits in the past thirty days.
Here we focus on one of two specific situations that call for the use of a comma before and:
(1) The Comma before and in Lists of Three or More Items
This hotly debated punctuation mark known as the serial comma is also often called the Oxford comma or the Harvard comma. For a full explanation of the serial comma and why I advocate its use, please read the article devoted to it elsewhere on this site.
(2) The Comma before and Joining Two Independent Clauses
An independent clause—also known as a main clause—is a group of words that comprises a subject and a verb and that can stand alone as a sentence. A compound sentence is one that contains two or more independent clauses joined by one or more coordinating conjunctions—most commonly, and.
In the following examples, the independent clauses appear in brackets:
- [Miguel took piano lessons for sixteen years], and [today he is an accomplished performer].
- [We rented lodging for our ski trip to Utah in March], and [later that same day we purchased airline tickets as well].
(Related bonus info: If we omitted the and in each of these sentences but kept the comma, we would end up with a type of run-on sentence called the comma splice.)
Notice in the next example that we do not use a comma before and because it does not join two independent clauses but merely joins two verbs:
- Miguel took piano lessons for sixteen years and today is an accomplished performer.
- We rented lodging for our ski trip to Utah in March and later that same day purchased airline tickets as well.
In each of these sentences, we have only one independent clause—two verbs (took and is in the first sentence and rented and purchased in the second sentence) but only one subject (Miguel and we).
And Is Not the Only Coordinating Conjunction
We need a comma when any of the seven coordinating conjunctions (and, but, or, nor, for, so, yet) join two independent clauses:
- [Tom is not taking his ski helmet on the trip], but [he is taking his new ski pants].
- [We are not concerned about the conditions on the slopes in March], for [the ski season in Utah typically runs through the middle of April].
Length Is Not a Factor
In this next example, even though the sentence is long, we do not need a comma because we have only one independent clause. The conjunction but merely connects the two verbs wanted and could not afford:
- Sigfried wanted to go back to school in August to earn a college degree but could not afford to quit his job and lose both his seniority and his benefits.
Some writers omit the comma before a coordinating conjunction if the two independent clauses are short, as in these examples:
- I drove home but he stayed there.
- The rains came and the rivers rose.
Omitting the comma in such cases is a perfectly acceptable stylistic choice. Nonetheless, although it is not necessary to use a comma before but or and in these sentences, it is not considered wrong to do so since we do, in fact, have two independent clauses in each sentence.
At the End of the Day, Clarity Rules
Sometimes a comma is necessary to prevent a misreading. Consider, for example, this sentence: “We often throw out garbage, and waste energy in doing so.”
Because the word waste can be a verb or a noun, the comma helps a reader avoid misreading it as noun in this sentence, where it is serving as a second verb.
Most people tend to overuse commas, however, so be sure your sentence is truly ripe for misreading before adding a comma in such situations.
Commas before and That Have Nothing to Do with the Conjunction Per Se
Sometimes we may see a comma before and (or another coordinating conjunction) that is appropriate for a reason unrelated to that conjunction.
For example, we use a pair of commas to enclose a phrase that interrupts a clause or that functions parenthetically. A writer may choose to place a comma before and (or any conjunction) when the conjunction launches such a phrase:
- Sarah told him again, and really meant it this time, to turn off the television.
- Alice asked John once, but only once, to forgive her.
We could argue that em dashes or parentheses would be a better choice, but that’s the topic of another article (the most popular one on this site).
Can you tell which of the following sentences need a comma before a coordinating conjunction because it joins two independent clauses?
- The ice storm last week caused tree limbs to fall on power lines and many people were without electricity for days.
- The ice storm last week caused many tree limbs to fall on power lines and left many people without electricity for days.
- Many companies are hiring chief information officers to oversee their information technology systems for only a specialist can keep pace with the rapid changes in technology.
- Shaniqua may stay on campus for the weekend or she may decide to go home to see her high school friends.
- Shaniqua may stay on campus for the weekend or may go home to see her high school friends.
- We knew the roads were becoming treacherous yet we dreaded having to announce that schools would be closed the next day.
- We knew the roads were becoming treacherous yet dreaded having to announce that schools would be closed the next day.
- [The ice storm last week caused tree limbs to fall on power lines], and [many people were without electricity for days].
- no comma
- [Many companies are hiring chief information officers to oversee their information technology systems], for [only a specialist can keep pace with the rapid changes in technology].
- [Shaniqua may stay on campus for the weekend], or [she may decide to go home to see her high school friends].
- no comma
- [We knew the roads were becoming treacherous], yet [we dreaded having to announce that schools would be closed the next day].
- no comma
©2004 Get It Write. Revised 2020.