how can I recognize the age of a cat ?

Cut off a leg and count the rings. Kind of like a tree.

count the rings like on a tree trunk, this only works with tabby cats though -j/k

I don't know how to tell, most vets will be able to give an estimate. I posted a link, (sorry about the pop-up). it gives ideas on how to tell cat age.

You can't tell exactly, but to estimate you would have to look at his size and whether he's really playful/energetic. Most of the time the teeth tell you the answer.

god i was gonna say the cut off the leg joke grrrr stealin my thunder

but seriously take it to the vet they can probably tell somehow

or ask who ever you adopted it from when it was born(but now im thinking youre asking about a stray you found?)

a vet can usually tell by its teeth

u can tell the owner that give it to u or go to the vet

teeth i think.