Doomed means fated to die or to have a very unfortunate outcome. You can also say you are doomed if you are certain that what is going to happen is going to be very unpleasant as well.
Ex: The first regiment of soldiers leading a charge are likely to sustain very heavy casualties. Those soldiers have to be very brave to charge into battle knowing that they are very likely doomed.
Ex: Johnnie said that when his mother found out he'd been missing school, she was going to be angrier than she'd ever been before. He told me that he was doomed, and although I tried to cheer him up, it didn't work.
If someone is always warning of bad or fatal outcomes, you would say that person is full of doom and gloom. Another term for that sort of extremely pessimistic person is prophet of doom.
Ex: I hope that John and Nico don't invite the Burdicks to their party. The two of them are such a drag ¬ he's always depressed, and she's even worse: always full of doom and gloom. It's impossible to have a good time when they're around.
The action of giving one item or service in order to receive another item or service is expressed by the verb to exchange. Exchange can also be used as a noun to refer to the action of trading one item for another or to the place where such actions occur.
Ex: For my birthday, my grandmother gave me a lovely jumper, but it doesn't fit me because it's a size too small. I'll have to pop into the shop and exchange it for a medium.
Ex: Many hostels offer book exchanges, where travelers can leave a book that they've already read and take a book that another traveler has left behind.
When speaking about financial matters, to exchange also refers to the act of changing money from one currency to another. The exchange rate is the value of one currency in relation to another.
Ex: It isn't a good idea to exchange dollars for euros at the airport. Those places offer unfavorable exchange rates because they know that some people don't plan ahead.
Ex: I don't think that I exchanged enough pounds for my trip, but I've notified my bank and can use my debit card to withdraw cash while I'm away.