Define temperature.

Answer

**Step-by-Step Solution:**

1. **Understanding Temperature**: Temperature is a physical quantity that expresses the degree of hotness or coldness of a body. It is a measure of the average kinetic energy of the particles in a substance.

2. **Measurement of Temperature**: Temperature is measured using various scales, the most common being Celsius (°C), Fahrenheit (°F), and Kelvin (K). For example, when we say a body has a temperature of 30 degrees Celsius, we are using the Celsius scale for measurement.

3. **Heat vs. Temperature**: It is important to note that temperature is not the same as heat. While temperature measures the average kinetic energy of particles, heat refers to the total energy transferred between bodies due to a temperature difference. Therefore, a higher temperature does not necessarily mean that a body contains more heat energy.

4. **Defining Temperature**: Based on the understanding above, we can define temperature as follows: "Temperature is the measure of the average kinetic energy of the particles in a substance, which reflects the degree of hotness or coldness of that substance."

**Final Definition**: Temperature is defined as the measure of heat energy present in a body, reflecting the average kinetic energy of its particles.

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