Strain, like stress, is a tensor. And like stress, strain is a tensor simply because it obeys the standard coordinate transformation principles of tensors. It can be written in any of several different forms as follows. They are all identical.

What is meant by strain tensor?

Strain tensors indicate just how and how much lines, areas, and volumes are stretched, i.e., the way neighboring material elements move near to or away from each other.

Is strain a vector quantity?

Strain is neither a scalar nor a vector. In the most general case it's a 2-dimensional symmetric tensor, defined by 9 numbers at any point. (Only 6 of the numbers are independent, because of the symmetry).