Hardly ever, rarely, scarcely and seldom are frequency adverbs. We can use them to refer to things that almost never happen, or do not happen very often. They have a negative meaning. We use them without not. Rarely, scarcely and seldom are more common in writing than in speaking:
He hardly ever smiles.
[a trout is a type of fish]
Providing fresh trout for dinner was rarely a problem.
She scarcely saw her grandchildren.
Griffin, the physics teacher, seldom shouted.
Hardly and scarcely meaning ‘almost not at all’
Hardly and scarcely can mean ‘almost not at all’ or ‘only just’. Hardly is much more common than scarcely, and scarcely is more formal:
Jen was so tired. She could scarcely keep her eyes open.
I hardly know them. I’ve only met them once.
We usually put these adverbs in mid position, between the subject and main verb, after the modal verb or first auxiliary verb, or after main verb be. In more formal styles, we put them in front position and invert the subject and verb. If there is no auxiliary or modal verb, we use do/does/did.
She hardly ever went on holiday.
Hardly ever did she go on holiday.
I had seldom seen so many people out on the streets.
Seldom had I seen so many people out on the streets.
Things are rarely as bad as you think they’re going to be.
Rarely are things as bad as you think they’re going to be.