Definition of multiple is :
In mathematics, a multiple is the product of any quantity and an integer. In other words, for the quantities a and b, we say that b is a multiple of a if b = na for some integer n, which is called the multiplier or coefficient (Wikipedia).
But in the definition of Eigenvector it is written that $Av$ is a scalar multiple of eigenvector $v$ . But $A $ is a matrix .
How can i relate $A$ with the definition of multiple that $A$ is an integer ?
The missing word is "integral". When you say one number is a multiple of another, you really typically mean that the one number is an integral multiple of the other.
So the descriptors "integral" and "scalar" qualify the multiplication involved.
In other words, it's a matter of context. These are not hard and fast rules, but conveniences of speech. You have to think about what is meant, not just blindly apply words without regard to intent.
There are many, many words used in mathematics with different meanings in different contexts (notoriously, "separable" is quite overused).