You use fixed to describe something which stays the same and does not or cannot vary.
They issue a fixed number of shares that trade publicly.
他们发行了固定数量的可公开交易的股票。
Many restaurants offer fixed-price menus.
很多餐馆提供套餐。
If you say that someone has fixed ideas or opinions, you mean that they do not often change their ideas and opinions, although perhaps they should.
people who have fixed ideas about things.
固执己见的人。
If someone has a fixed smile on their face, they are smiling even though they do not feel happy or pleased.
I had to go through the rest of the evening with a fixed smile on my face.
我不得不挂着僵硬的笑容度过那晚余下的时间。
no fixed abode , no fixed address
Someone who is of no fixed abode or no fixed address does not have a permanent place to live.
They are not able to get a job interview because they have no fixed address.
他们无法获得工作面试的机会,因为他们居无定所。