as a noun, 'long' refers to a long period of time.
It won't be for long.
I haven't seen him in a long.
It's been a long since we last met.
When 'long' is used as a noun, it's often in idiomatic expressions or set phrases.
As an adjective, 'long' describes the extent or duration of something in terms of length or time.
She has long hair.
It was a long journey.
I've had a long day at work.
'Long' can be used in comparative forms like 'longer' and superlative forms like 'longest.'
as a verb, 'long' means to have a strong desire or yearning for something.
I long for the days when we were together.
She longed to see her family again.
He longs for some peace and quiet.
'Long' as a verb is often followed by 'for' or 'to' + verb.
as an adverb, 'long' describes the duration or extent of an action.
How long have you been waiting?
She hasn't been here long.
I won't be gone long.
When used as an adverb, 'long' often answers the question 'how long?'