不可数名词，不加“S”。可数名词加“S”

可数就是有单复数之别。如orange(s),banana(s).
不可数没有单复数之别，但要在前加形容词。如water,a lot of water.

a cup of water,
two litres of water, ...
a piece of cake,
....
Uncountable nouns can be expressed as if it could be counted....

可数名字后面直接加s或es，还有就是个别的单复同形..
不可数名字像money，water就不能加s了
eg：some money a glass of water