fairly : 语意最弱，多用于褒义，表示适度地、尚可的意思。不可与too或比较级连用。
- She's fairly tall.
- I'm fairly sure that this is the right address.
- We get on fairly well.
- I saw her fairly recently.
pretty : 用法与rather相似。常用于非正式文体。
- The house has four bedrooms, so it's pretty big.
- I'm pretty sure it was her.
- I've got a pretty good idea of how to get there.
- I'm quite tired but I can certainly walk a little further.
- There was quite a lot of traffic today but yesterday was even busier.
- It was quite a difficult job.
- He's quite attractive but not what I'd call gorgeous.
- It would be quite a nuisance to write to everyone.
- It's rather cold today, isn't it?
- That's rather a difficult book - here's an easier one for you.
- The train was rather too crowded for a comfortable journey.
- She answered the phone rather sleepily.
- I rather doubt I'll be able to come to your party.