Temperature is a measurement of how hot or cold something is. When you check the temperature outside, you're finding out whether you need a jacket or can wear shorts. When you have a fever, a thermometer measures your body's temperature to see if it's higher than the normal 98.6 degrees Fahrenheit.

Scientists define temperature as the average energy of moving molecules in a substance. In hot coffee, molecules bounce around rapidly. In ice cream, they move much more slowly. The faster molecules move, the higher the temperature feels.

Temperature affects almost everything around you. Water freezes into ice at 32°F (0°C) and boils into steam at 212°F (100°C). Bread dough rises faster in a warm kitchen than a cold one. Metal expands when heated and contracts when cooled, which is why bridges have special joints to handle temperature changes.

We measure temperature with thermometers using different scales. Americans typically use Fahrenheit, while most other countries use Celsius. Scientists often use Kelvin, which starts at absolute zero, the coldest possible temperature, where molecules barely move at all.

The word can also describe the general mood or feeling of a situation. A teacher might try to lower the temperature in a heated classroom argument, or you might sense the temperature rising when two friends start disagreeing about which game to play.