- fish OR fishes?
The plural of fish is usually fish: ‘a fish’, ‘three fish’. Fishes is used to refer to different species of fish.
- it’s OR its?
The confusion between it’s and its occurs because ’s indicates possession, so English speakers naturally want to use it’s to mean ‘something belonging to it’. But it’s is only used when it is a contraction of ‘it is’ or ‘it has’. Otherwise, it is always its.