"This girl is nine years old."
Translation:Esta niña tiene nueve años.
Why is this "tiene nueve años" and not "esta nueve años" or something that uses the word "is" and not "has"
Because in Spanish you say How many years do you have? I have 9 years. In Spanish that is the same as How old are you? I am 9 years old, in English. But it would not be correct to say I am 9 years old in Spanish, just the same as it would not be correct to say I have 9 years. . . in English. Hope that makes sense