What is a constant in algebra?

A constant is a rate of change, or something that can be predicted. For example; numbers of days in a week are constant, aging is constant, the hours in a day are constant, and the time it takes for the light to turn on is constant.

The constant is usually represented at the end of an equation. For example; 2x + 4; 4 is the constant. In (2x^2 + 7x - 9), - 9 is the constant.

A number in an equation that is by itself