# A question about age comparison

John has two daughters, S and X.
S = 18 years old
X = 9 years old

Now, if I want to compare their ages, how do you say it naturally?

I have written these three sentences, do they sound good to native speakers?

Sentence 1:
S's age is twice as old as X's age

Sentence 2:
S's age is twice X's age

Sentence 3:
S's age is 2 times older than X's

• You do it by not using the word age. John is twice as old as Jane. Forget the word age in the comparative. – Lambie Jul 27 '17 at 18:33
• Of course, you don't have to forget about using age. What's wrong with "S is twice X's age"? – Robusto Jul 27 '17 at 20:27
• It's a little off-topic but might be helpful to OP to point out that in conversation, "S is twice X's age" can also be used less literally to describe a great age disparity which might not necessarily be exactly 200%. If I heard someone say that, I'd assume that S is anywhere from, say, 1.5x to 3x as old as X. YMMV - some people are more precise in their wording than others. – A C Jul 27 '17 at 20:42
• @Robusto I think Lambie’s point wasn’t that the word age should necessarily be left out entirely, but that it’s unnatural in the comparative bit (or more precisely, in the subject of the comparator). “S is twice X’s age” is fine, but “S’s age is twice X’s age” is clumsy and unnatural. – Janus Bahs Jacquet Jul 28 '17 at 7:58
• Sentence 3 is not correct because: A person has an age. A person can be older (or younger). But your third sentence says the person's age is older, as if the age has an age of its own. – Tim Pederick Jul 28 '17 at 13:42

Of the sentences you've suggested, the only one that makes sense is

S's age is twice X's age.

A more common way to say it would be:

S is twice X's age.

However, the sentence that I would use is:

S is twice as old as X.

• Or, instead of "S's age is twice X's age", might I suggest omitting the first age and saying "S is twice X's age"? – A. Galloway Jul 27 '17 at 17:40
• @A.Galloway thanks, I've added that. I was so focused on that being the only meaningful choice that I missed that way to make it more idiomatic. – user34258 Jul 27 '17 at 18:57

S is twice as old as X

That's valid.

Also valid is:

S is twice X's age.

Ex:

Scott: "Did he ask her out?"
Andrew: "Of course not.. he's twice her age!"

"S's age is twice as old as X's age" - There is a fatal error. S and X are young or old. S's age and X's age are not. Same as saying "my name is called John". Wrong, my name isn't called anything. My name doesn't have a name. I have a name, but my name hasn't. I have an age, but my age doesn't. And sentence 3 has a very similar problem.

"S's age is twice X's age" is Ok. Sentence 1 and 3 can be fixed by not comparing how old their ages are, but how old the people are. "S is twice as old as X" is fine, so is "S is two times older than X".