Generally, you should not use a comma before or after "either" when acting as a conjunction, determiner, or pronoun. However, when acting as an adverb (to agree with a negative statement), the use of comma before "either" is optional.
When used as a conjunction, determiner, or pronoun, we do not generally include a comma before or after "either".
I will buy either the black one or the red one.
Typically used to agree with a negative statement, the comma before the adverb "either" is optional.
I don't like reading long novels, either.
At the beginning of a sentence, the phrase "in either case" is often followed by a comma.
You can go to Indonesia or India. In either case, renew your passport this month.
Contents
1. Different Ways to Use Either
"Either" can be a conjunction, a determiner, a pronoun, or an adverb.
- Either/Or (correlative conjunction). The pair either/or means "one or another" (e.g., "Buy either the watch or the ring.")
- "Either + singular noun". As a determiner, "either" means "whichever of two" (e.g., "Buy either car."). It can also mean "each of two" (e.g., "There's a motel on either side of the road.").
- Pronoun. As a pronoun, "either" means "one or another" (e.g., "Both girls are cute. I would date either.")
- "Either of...". You can also use the structures "either of + plural pronoun" or "either of + determiner + plural noun" to say "one or another" (e.g., "Either of those devices is reliable.")
- Agreeing with a negative statement (adverb). (e.g., "I didn't enjoy the party, either.")
- "In either case" means "in one case or the other" (e.g. "He may be French or German. In either case, his English is good!")
2. A Comma Before 'Either' is Often Unnecessary
2.1 Either/Or (correlative conjunction)
As a correlative conjunction, the pair either/or connects two positive statements of equal weight. We do not commonly need a comma before or after a correlative conjunction, such as either/or.
I can buy either the red shirt or the pink shirt.
A comma is required, however, to separate two independent clauses (part of a sentence with a subject and a verb that can stand alone) when using "either/or".
Either you clean the room, or you do your homework.
More examples
- I think Alberto is either Colombian or Peruvian.
- She can either pay online or pay in person.
- I need to buy either a laptop computer or a desktop computer.
2.2 Either + singular noun (determiner)
As a determiner, we use either with the structure "either + singular noun" to mean "whichever of two" or "each of two".
Can we have the next meeting on Thursday or on Friday? Either day is ok with me.
In this situation, we must not use a comma after "either".
There are many oak trees on either side of the river.
More examples
- The seats on either side of me were empty.
- Do you like the black car or the white car? Either car is fine.
- Many houses were built on either side of the street.
2.3 Pronoun
We do not usually place a comma before or after the pronoun "either".
Do you prefer to visit Thailand or Vietnam? Either is fine.
More examples
- Do you want to watch a horror movie or a comedy? Either is ok.
- Which book do you want? Either is fine.
- Which purse do you want to buy? Either!
2.4 Either of
Either of + plural pronoun
We do not normally add a comma when using the structure "either of + them/us/theirs/ours".
I'm waiting for Claire and Jennifer. Has either of them called?
Either of + determiner + plural noun
When using "either" and a determiner (my, your, his, these, those, the, etc.) followed by a plural noun, commas are also generally unnecessary.
You can wear either of those T-shirts.
More examples
- Either of us can go.
- Which ring do you like? Either of them are perfect.
- You can use either of my hats.
3. When to Use a Comma Before or After 'Either'
3.1 Agreeing with a negative statement (adverb)
We can use "either" to agree with a negative statement. Some writers place a comma before the adverb "either", whereas others do not.
I think Gabriel is not Spanish. Well, he is not Italian either.
I think Gabriel is not Spanish. Well, he is not Italian, either.
More examples
- I didn't enjoy the party either.
- Alice hasn't been to Paris, either.
- James cannot swim either.
3.2 Commas with 'In either case'
The prepositional phrase "in either case" means "one case or the other". When using "in either case" as an introductory phrase, we frequently add a comma after it.
She looks Russian or Ukrainian. In either case, her English is excellent.
At the end of a sentence, however, we do not typically use a comma before "in either case".
I'm not convinced whether to go to France or Spain. I will go to Europe in either case.
More examples
- My girlfriend and I are thinking about a trip to Thailand or Myanmar. In either case, we will visit its Buddhist temples and national parks.
- It may be a hardware or a software problem. You should call a qualified service in either case.
- These strategies are rational in either case.
