“Let's crack open a window and get some fresh air in here.”
Your apartment is hot and has a little bit of a bad smell. You think that you should open one of the windows, so you say this to your roommate.
Let's crack open a window and get some fresh air in here.
The phrase "Let's ___" is well-known to English learners. However, learners often over-use "Let's ___" and use it in situations where it isn't appropriate.
When can you say "Let's ___"? You usually use it when you're suggesting something that you're sure the listener will accept. If you're meeting a friend for lunch, then you're sure that they will agree to eat with you. So you can say:
In situations where you're not sure how the listener will respond to your suggestion, you can use other phrases like "Would you like to ___?", "Why don't we ___?" or "We should ___":
Would you like to go out to dinner with me some time?
Why don't we meet at 7:30?
We should get together some time and have a drink.
To "crack open" a window means to open it a little bit. However, sometimes people say "crack open" just to sound cool, when actually they mean to open something completely.
Other things that you can "crack open" include:
Come on over! We'll crack open a bottle of wine and cook some steak on the grill.
I saw him crack open the door and look out.
"Fresh air" is air that:
- comes from outside
- is clean
- doesn't smell bad
- is dry and cool
Air that you breathe out in the countryside on a cool, sunny day is the perfect example of "fresh air". But if you're riding in a dirty car with no air conditioning in the summer, then you might call the air from outside the car "fresh", even if it's dirty and warm.
When people want to breathe fresh air, they say "I want to get some fresh air." If they're in a room or car, they might say "Let's get some fresh air in here."