Do I put an apostrophe in parents in this sentence? His parents went to a Chinese restaurant to celebrate their anniversary.

No.

The word “parents” signifies both parents. The word “parent’s” would signify something owned by one of those parents.

No. “Parents” in the sentence is not possessive, thus no apostrophe needed.

Where you would use an apostrophe, because it is possessive, is “It was his parents’ anniversary.”

@crisw

Yes, IF you were speaking of something owned by both parents. : )

I’m joining the chorus here because I’m big fan example sentences.

His parents went to a Chinese restaurant to celebrate their anniversary

No, apostrophe “parents” is plural there

compared to the plural possessive:

He went to his parents’ Chinese restaurant to celebrate their anniversary.

if, as @crisw said, the restaurant is owned by both parents

and

compared to the singular possessive:

Having a child throw a major tantrum at a restaurant can be a parent’s worst nightmare.

An apostrophe is almost always used to indicate a possessive form or to take the place of the “missing” letters in a contraction.

No. The apostrophe is not used to form a plural.

I know you see it done everywhere these days, such as on signs like these:

  Fresh-Picked Apple’s
  Open Sunday’s
  Employee’s Only
  Puppie’s For Sale

Here’s the thing: the people who made those signs did it wrong. Don’t copy them. They are not models of good English. No matter how many times you see them, they are still ignorant and wrong.

Nope. Using an apostrophe signifies possession.

My parents are cool. (the parents aren’t “possessing” anything)
I had to deal with a parent’s death. (possessive because it is the death of or belonging to a parent)

@Jeruba is our great champion and protector of the English language and is sadly, on target here. A whole lot of people making the same mistake over and over does not turn something that is grammatically incorrect or misspelled into something that is.

It just occured to me that there’s another time when you might want to use an apostrophe… when you are discussing an aspect of one of your parents, as in, “My parent’s a nut!” ( Parent’s = parent is. ) Even though I don’t think this is accepted practice, it is used from time to time.

No, and thank you very, very much for asking. Most people treat apostrophes like garbage. If you ever have a doubt in the future, be quick to ask us!

No, the sentence you typed is correct.

No. Parents is plural there.