norm
An unwritten rule about how people usually behave in groups.
A norm is a standard or expectation that most people in a group follow. Norms are the unwritten rules that guide how people behave: raising your hand before speaking in class is a norm, as is saying “thank you” when someone helps you or holding the door open for the person behind you.
Every group has its own norms. Your family might have norms about dinner time or bedtime. Your classroom has norms about how to treat shared materials. Different sports have different norms: in baseball, it's normal to keep quiet while the pitcher throws, but in basketball, fans make as much noise as possible during free throws.
Norms aren't laws. Nobody gets arrested for breaking them, but they create expectations. When someone goes against a norm, others often notice and feel uncomfortable. If a student suddenly started shouting answers without raising their hand, they'd be violating classroom norms.
The word can also describe what's typical or average. When a doctor says your height is normal for your age, they mean you're growing at the usual rate. Scientists talk about normal temperatures or normal rainfall for a region. In mathematics, a line that's normal to a surface means it stands perpendicular to that surface, at a perfect right angle.
Understanding norms helps you navigate different situations. The norms at a library differ from those at a playground, and recognizing those differences shows social awareness.