“Why don't we exchange business cards?”
You're at a business networking event, and you meet someone who you might like to do business with in the future. You want to keep in touch with them. Near the end of the conversation, you say this.
Why don't we exchange business cards?
This is a way to make a suggestion to do something together. You use this when you expect the listener to agree with you:
I don't feel like cooking tonight. Why don't we order something out?
Why don't we make a deal: if I help you with this, you have to promise to come to my game on Sunday.
When you "exchange" something with a person, you give them something and they give something back to you. In the example above, the speaker suggests exchanging business cards. That means that each person gives the other person their business card.
Other words that people often use with "exchange" are:
- exchange phone numbers
- exchange ideas
- exchange a glance (this means to look at each other secretly to communicate a message)
- exchange words (this means to get into an argument)