Countable Noun

Yes, depending on the context and meaning in a sentence, a noun can be both, countable and uncountable. Such nouns are called dual-use nouns and their countability depends on how they're being used.

For example:

·       Here hair is very long (uncountable)

·       There are three hairs in my soup. (countable- refers to individual strands)

Try putting a number in front of a noun or make it plural. If it works, its countable; if it doesn't, it is probably uncountable.

For example:

Bus: There are fifteen buses in my school. (Correct)

Anxiety: I felt two anxious. (Incorrect as it is uncountable)

Abstract nouns are usually not countable, however, they can be countable in specific contexts.

For example:

·       He had two brilliant ideas.

·       She gave me a piece of information.

Some of the quantifiers that are used with countable nouns include- many, few, a few, several, each, every, some, any.

Examples:

·       There are many buses in the stand.

·       I kept a few chairs in the room.

·       There are several people in the park.

Yes, 'a' or 'an' is used with only singular countable nouns, not plurals.

For instance:

·       A cat is climbing up the tree.

·       There is an apple in the fridge.

·       There is a bus on the road.