Without more information, the age of your cat cannot easily be determined. Do you know how old the cat was when you got him or her? Or did you see their birth? Do you know where they lived before hand? If you don’t know how old your cat was when you got them, the vet can probably help you estimate how old the cat is. If the cat is older, other signs will probably start to show up sooner than later.
The cat will also act differently if it is younger rather than older. Kitties typically meow in captivity, but not in the wild. They rub up against you to get attention, while older cats can be a little stingier with who they rub up against or let pet them.