If a term consists of only variables, its coefficient is 1. Constants Constants are the terms in the algebraic expression that contain only numbers. That is, they're the terms without variables. We call them constants because their value never changes, since there are no variables in the term that can change its value. In algebra, we work with the set of real numbers, which we can model using a number line.
Real numbers describe real-world quantities such as amounts, distances, age, temperature, and so on.
A real number can be an integer, a fraction, or a decimal. They can also be either rational or irrational. Imaginary numbers are used by mathematicians to describe numbers that cannot be found on the number line. They are a more complex subject than we will work with here. Since three can be expressed as three over one, or the ratio of 3 to one, it is also a rational number.