A "deposit" is some money that you pay at first when you're reserving something. You might need to pay a "deposit" in situations like:
- when renting a car
- when signing up for classes
- when renting an apartment
You can express the amount of a deposit like this:
a $400 deposit
a 10% deposit
Sometimes a deposit is "non-refundable". This means that you can't get the deposit back after you've paid it.