Expressing someone's age

Les pièges de l'expression de l'âge. On emploie en anglais le verbe BE (être).

How old are you? I am 10. Are you 12? He is 14. She is 1 month old. It is 500 years old, they are the same age...

Il y a deux solutions : He is 12. ou He is 12 years old — mais pas « He is 12 years ».