fairly - rather - quite
By the end of the day we were rather tired.
The film wasn’t great but it was quite exciting.
and in informal English: pretty
We had a pretty good time at the party.
We call these words mitigators.
We use these words and phrases as mitigators:
a bit - just a bit - a little - a little bit - just a little bit - rather - slightly
She’s a bit younger than I am.
It takes two hours on the train but it is a little bit longer by road
This one is rather bigger.
This is a slightly more expensive model than that.
This is rather bigger one than that.
Adjectives as intensifiers:
total - complete
utter - perfect
He’s a complete idiot.
They were talking utter nonsense.
… but we do not say:
The idiot was complete.
The nonsense they were talking was utter.