Animals can be grouped in many ways.

Animals can be grouped in  many ways according to their external features.
A group of animals can be divided again into different groups.
For example, the animals below are grouped into one group because each of them has four legs and a tail.

Tigers and lions have claws and fur. Goats and cows have horns and hair.

So, we can group these animals into two different groups.

Animals with claws and fur

Animals with horns and hair