1. Most boys grow a lot between the age of 9 and 14.

2. Most boys grow a lot between the ages of 9 and 14.

(Which one is correct? Do we have to use 'ages' or 'age' in the sentence?)

ages, im 90% sure

Yes, #2 is correct.

Both sentences are grammatically correct, but they convey slightly different meanings.

1. "Most boys grow a lot between the age of 9 and 14."

This sentence suggests that boys experience significant growth during a specific period, which is between the singular age of 9 and 14. It implies that boys experience growth during a single age, which is 9 and continues until 14.

2. "Most boys grow a lot between the ages of 9 and 14."

This sentence indicates that boys experience growth over a range of ages, specifically from the ages of 9 to 14. It recognizes that growth occurs throughout this age range and not limited to a specific age.

While both sentences are grammatically correct, the second sentence, using "ages," is more commonly used and accurately reflects the continuous growth that boys experience between the ages of 9 and 14.