Question

what is mean by average atomic mass ​

Answer 1

In nature there are different allatrop of a single element

Example

C12 and C14 are allatrop of carbon

here

the atomic Mass of C12 and C14 is different which is 12 and 14

hence,

to get a single atomic Mass average is taken into consideration such average of atomic Mass is known as Average atomic Mass

In short

Average of atomic Mass of all allatrop of that element is called as Average atomic Mass.

hope it helps...