The word high has several meanings:

1. Far above the ground or a reference point. A high mountain peak towers over the valley below. An airplane flies high in the sky. When you climb to the top of a tall tree, you're up high. The opposite of high in this sense is low.
2. Greater than normal in amount, degree, or intensity. A student might receive high marks on an excellent test. A thermometer shows a high temperature on a hot summer day. A restaurant might charge high prices. When the stakes are high, there's a lot to gain or lose.
3. Advanced or important in rank or quality. A high court makes significant legal decisions. Someone in a high position at a company has considerable authority and responsibility.

The word appears in many common expressions. When emotions run high, people feel things intensely. High tide is when ocean water reaches its highest point on the shore. A high note in music has a pitch that sounds elevated and clear. When you hold your head high, you feel proud and confident. And when you search high and low for something, you look absolutely everywhere.