Which kinds of vegetable can you see in these photographs?
These vegetables are: garlic cloves, spinach and carrots.
Very good, Maribel!
These vegetables are: garlic, spinach and carrots.
Great Job! :)
Words like cabbage, garlic, spinach, lettuce are collective nouns.
They do not change they can't be: garlics, spinaches or lettuces.
A collective noun is any noun that describes a collective, one simple example "garlic." Garlic consists of garlic cloves, spinach of spinach leaves. There are also mass nouns.
Mass nouns are different, they consist of words such as "water" or "air" which are usually not pluralized.
I think it would help to understand other English words too.