Petty means small-minded and concerned with unimportant things, especially when it comes to criticizing others or holding grudges. A petty person might stay angry at a friend for weeks because they forgot to save them a seat at lunch, or refuse to speak to a sibling because they borrowed a pencil without asking. The word captures that sense of making a big deal out of something that really doesn't matter much.

You might hear someone say “Don't be so petty” when a person is dwelling on tiny slights or insults instead of focusing on what's actually important. If two classmates have a serious disagreement about a group project but then one of them starts complaining about how the other chews gum too loudly, that's being petty: bringing up trivial annoyances instead of dealing with the real issue.

The word can also describe actual smallness or insignificance. A petty thief steals small items rather than planning major robberies. Petty cash is a small amount of money kept on hand for minor expenses.

When someone acts petty, they're usually letting small irritations control their behavior and damage their relationships over things that won't matter tomorrow, let alone next year.