why sheep can also be used in an plural form and why not sheeps
eg:- robbers came in stole away the sheep
the noun "sheep" has the same form both in the singular and in the plural. It depends on the context you use it in.
The sheep are in the field.[plural]
That is the sheep I bought yesterday.[ singular]
This is called "zero plural"
other examples :
1 Chinese - 2 Chinese
1 species - 2 species