Given a text, write a compressed version of it in a single sentence.
Q: A custom, often expressed only after it occurs, of giving a little extra when making a transaction or closing a bargain. For instance, when buying candy, the vendor may add one extra piece, de pilon, to surprise and make a child happy.
A:
A custom, often expressed only after it occurs, of giving a little extra when making a transaction or closing a bargain.