Addendum

An addendum is like an extra part that is added to something that you have already written or signed. It's like when you draw a picture and realize you forgot to add something, so you draw it in the margin.

For example, imagine you wrote a contract with your friend to borrow their bike for a month. Then, you remember that you also want to borrow their helmet too. So, you write a little note on the bottom of the contract saying "Addendum: I would also like to borrow your helmet for the month."

Basically, an addendum is a way to make changes to a document or agreement after it has already been written or signed. It's like a mini revision or addition.