An assumption is something you believe to be true without having proof. When you assume something, you're filling in missing information with your best guess about what's probably true.

Imagine your friend doesn't show up to meet you at the park. You might assume she forgot, got sick, or had to help her parents with something. You don't actually know why she's absent, but you're making assumptions based on what seems likely. Sometimes assumptions turn out correct, and sometimes they don't. Maybe she's actually planning a surprise party for you!

We make assumptions constantly because we can't know everything. When you sit in a chair, you assume it will hold your weight. When you hand in homework, you assume your teacher will read it. These everyday assumptions usually prove correct, which is why we rely on them.

Problems arise when we assume things about people without knowing the facts. If you assume your classmate is unfriendly just because she's quiet, you might miss the chance to make a great friend. Scientists work hard to test their assumptions with experiments rather than just accepting them as true.

The phrase “don't make assumptions” reminds us to ask questions and gather facts before jumping to conclusions. Assuming can save time, but it can also lead us astray when we guess wrong about important things.