what is a constant variable in science

In science, a constant variable, also known as a control variable, is a variable that is kept the same during an experiment. The purpose of a constant variable is to ensure that any changes in the dependent variable are due to changes in the independent variable, and not due to changes in other factors. Examples of constant variables in science include temperature, humidity, pressure, experiment duration, sample volume, and the technique of the experiment. Constants are values that should not change either during or between experiments. Many natural forces and properties, such as the speed of light and the atomic weight of gold, are experimental constants. In some cases, a property can be considered constant for the purposes of an experiment even though it technically could change under certain circumstances. It is important to note that constants are different from controls, which are groups that are exposed to "normal" conditions in an experiment.