"It is not a cat."
अनुवाद:यह एक बिल्ली नहीं है।
Animals (and even little babies) are mostly addressed as "it". It is cat, It is a baby.
Technically यह एक बिल्ली नहीं है could mean:
It is not a cat, He is not a cat, or She is not a cat.
In English we don't have genders, so the cat could be male or female. If you aren't sure then you can also say 'It'.