phrase usage - Can you use "Both" alone in this case?

If somebody tells me :

Do you like summer or winter ?

Is it correct if I answer :

Both.

Or am I forced to say :

Both of them.

Thank you.

Answer

As @jimsug said, they are both fine.

The word both functions as a pronoun in both of your responses: "Both." and "Both of them."

I'd like to quote this explanation along with an important usage note from Macmillan dictionary:

Both can be used in the following ways:
as a determiner (followed by a noun, but not by a pronoun): Both children are at school.
as a predeterminer (followed by a word such as "the," "this," "his," etc.): I like both these pictures. ♦ Both her children are boys.
as a pronoun: Both arrived at the same time. (followed by "of"): Both of them are learning English. (after a noun or pronoun subject): The twins both have black hair. (following a pronoun object): I like them both. (after a modal or auxiliary verb, or after the verb "to be"): We can both speak Spanish. ♦ They are both good singers.
in the expression both...and...: a method that is both simple and effective

Usage note: both
Do not use both in negative sentences. Use neither: Neither of my parents wanted me to leave school (=my mother did not and my father did not).