How do you know if singular or plural is used after the word "their?"

For example, consider the following sentence:
"Rockers like Pink and celebs like Pam Anderson show their soft side in pet portraits." (sentence taken from today's Yahoo home page)

Why is it not "their soft sides"?

Consider "Couples spend a lot of money in a very short amount of time on their honeymoons." (New York Times)

Why not "their honeymoon"?

"their" is a plural pronoun. the first sentence about the rockers is grammatically incorrect; it should be "their soft sides"

that's why when writing a formal paper, and you're writing about a specific person, you're always supposed to use "he or she" instead of "their"

when using the pronoun "their", all possessions are supposed to be plural.

hope this helps!

"Their" shows possession of more than one individual in the third person. Whether the word to follow is singular or plural has nothing to do with the word "their", but whether the word itself should be singular or plural. In your first example, "their" refers to Pink and Pam Anderson. "Soft side" is a naturally singular term. This is common with nouns that refer to some emotional state.Think of the noun, happiness. There can't be different happinesses because you are describing an emotional state.

In your second sentence, it could be "their honeymoon" depending on the intended meaning. You would use "their honeymoon" if every couple were taking the same exact honeymoon at the same time. However, "their honeymoons" refers to different couples taking different honeymoons.

So both sentences are correct.

Example: The neigbors said their dog is missing. (Referring to one dog, but showing multiple possession of one dog)
The neigbors said their dogs are missing. (Referring to two or more dogs)

Because the noun that "their" is refurring to is singular (one Pamela Anderson) in the first sentence and plural in the second (2 people in a couple).

Although "celebrities" is plural "their" directly points to Pam

guess the former should be 'sides'

The reference is to Pink as well as Pamela Anderson, hence it is plural. It should be their soft sides.

It may not be considered a grammatical error though. Reason: The use of the word 'portraits' refers to plural. It is assumed that the writer is indeed talking about the sides of both the women in their portraits.

I think, for the first one, each has only one soft side so it's singular.

For the second, some couples have multiple honeymoons so they used plural.