'to turn against' means to change opinion to not liking or agreeing with someone or something.
- Since they declared war, the country has turned against the government.
- He is always spreading nasty stories in an attempt to turn everyone against me.
'to turn around' means to turn so that you are facing the opposite direction.
- When I'm speaking to you, turn around and look at me.
- I recognised him even from behind. He didn't need to turn around so I could see his face.
'to turn someone away' means to refuse them entry to a place.
- We only have fifty places so we have to turn people away every day.
- The restaurant has a strict dress code. It turns away anyone in shorts and T-shirt.
'to turn away' also means to refuse to help someone.
- Nobody is turned away. We help everyone who comes to us.
- He's my nephew, I can't turn him away without giving him some money.
'to turn back' means to fold a part of something so that it covers another part.
- She marked her place in the book by turning back the page.
- When we arrived in the room, the maid had turned back the bedcovers.
'to turn back' also means to return to the place you came from.
- The road was impassable after the snow so we had to turn back.
- I forgot to pick up the street map and guide book so we had to turn back and go get them.
'to turn back' also means to change your plans.
- There was no turning back once she had said she was going to do it.
- We have invested a lot of time and money in this project, there's no turning back now.
'to turn down' means to refuse something.
- He was offered a job there but he turned it down as it was too far from home.
- I turned down an invitation to dinner to come and spend the evening with you.
'to turn down' also means to reduce the amount of heat or sound produced.
- Turn the TV down. It is far too loud.
- It's rather hot in here. Shall I turn the heating down now?
'to turn in' means to give something to someone in authority to deal with it.
- To get a new driver's licence, I had to turn in my old one.
- There was an amnesty and you could turn in guns and knives without any consequence.