Temperature is defined as the degree of hotness or coldness, as measured on a definite scale. Three temperature scales are in general use today:

The Fahrenheit (°F) temperature scale is used in the United States and a few other English-speaking countries.

The Celsius (°C) temperature scale is standard in virtually all countries that have adopted the metric system of measurement, and it is widely used in the sciences.

The Kelvin (K) scale, an absolute temperature scale (obtained by shifting the Celsius scale by −273.15° so that absolute zero coincides with 0 K), is recognized as the international standard for scientific temperature measurement.

Common temperature measurements in each scale:

The conversion of temperature readings from one scale to another can be easily calculated using the following formulas: 

Many different types of thermometers, both analog and digital are available for a variety of purposes and applications. The complete Sper Scientific line of thermometers are available here.