A/the/no article rush

"rush" is actually a countable noun, though "in a rush" is a set pattern of words, and "in rushes", for example, would not be used.

Which rule do we use here to say it's a countable noun? Can we put numbers before it?

Jigneshbharati Which rule do we use here to say it's a countable noun?

The fact that it is preceded by the indefinite article. Also the fact that it cannot be used without an article or other determiner.

Your answer makes sense when you read English written by experts but in order to know which article to use one needs to be competent to identify countable nouns. Can you count "rush"? Sorry I just want clear my doubt and please forgive my ignorance.

JigneshbharatiCan you count "rush"?

There aren't too many real-life situations in which you would talk about "two rushes","three rushes", etc., but it is possible. Most Google hits seem to be in the special context of American football. Pluralisation sometimes occurs; for example you can talk about "rushes of passion", "rushes of blood to the head", and so for

GPYand "in rushes", for example, would not be used.

I mean, would not be used in exactly that way. For example, you would not say that a group of people were "in rushes" to mean that they were hurrying. "in rushes" can be used in other contexts, e.g. "His breath came in rushes".