Their titles explain almost everything we need to know about them. There are nouns that we can count and there are ones that we cannot count.
Countable nouns, like their title suggests, can be counted. They have both singular and plural forms.
Star – Stars
Book – Books
Computer – Computers
Church – Churches
These cannot be counted, as in, they don’t have singular or plural forms. They only have one form, i.e., their original form. When using them in a sentence, be sure not to add “a/an” before uncountable nouns as they don’t have a singular form. Also, you cannot add “s” or “es” at the end of uncountable nouns as they don’t have a plural form either.
Water – you cannot say “waters” or “a water.” You can only say water.
Furniture – you don’t say “furnitures” or “a furniture.” You just say furniture.
Remember, uncountable nouns always go alone. They don’t get “a” or “an” before them. They can be accompanied by determiners like some, a lot of, the, etc. Otherwise, they go alone.