Could singular nouns be uncountable?

Question

From English Grammar Today on Cambridge Dictionary

Countable nouns can be singular or plural.

Which implies singular nouns is a type of countable nouns. Other parts in that tutorial justifies this.

However, Collins says

Singular nouns that are uncountable are used without a determiner when you are making a general reference.

Could singular nouns be uncountable? If yes, in what kind of situations they could be?

It seems that it's meaningful to distinguish singular or plural in terms of countable nouns. Which means that if a word is uncountable, it's not countable, therefor it's neither singular nor plural?

Is my understanding correct?

Answer 1

Uncountable nouns are usually singular.

When speaking of grammar, "singular" is a grammatical class, and most uncountable nouns have a singular form and agree with a singular verb. The grammatical class of "singular" nouns is related to the meaning "one of the object" when the noun refers to a countable object.

So:

Beer is a good drink.

(The uncountable noun beer is singular and agrees with the singular form of the verb "is")

A cat is walking on the fence.

(The countable noun "cat" is singular)

Beer can also be used as a countable noun (meaning "a glass of beer")

Three beers are on the table.

Here the countable noun "beer" is plural and has the plural noun "are".

There are a few words that are only plural, and act a little like uncountable nouns, but have plural agreement.

My belongings are on the table.