# Term

In an algebraic expression, the objects separated by operation symbols (+, -, =, etc.) are referred to as terms. In the expression below,

2x2 - (x + 4)y + 3

2x2, (x + 4)y, and 3, are all terms. Expressions are made up of one or more terms, while equations are expressions that are separated by an equals sign.

## Types of terms

The terms that make up an expression are most typically made up of a combination of constants, variables, and coefficients.

### Constant

Constants are fixed quantities. They are well-defined quantities that do not vary, unlike variables. Examples of constants include numbers such as 0, 1, π, e, and more. π and e are two of the most widely used mathematical constants. Even though both π and e are irrational numbers, meaning that we can't express them as a ratio of two integers, they are still mathematical constants because their values, even if we can't write them explicitly, stay the same. π will always be the ratio of a circle's circumference to its diameter.

In generalized algebraic expressions or equations, constants are commonly denoted using "c," though other letters such as "k" are also used.

### Variable

Variables are symbols used to represent unknown values. Some of the most commonly used symbols are x, y, z and t. Often, a variable may be named after the first letter of the object in question. For example, an unknown radius of a circle may be represented using the letter "r."

Variables are used as part of expressions to indicate a relationship between the terms of the expression or equation. For example, in the equation x = 3y, we don't know the value of x or y, but we know that x is 3 times of y because of the coefficient of 3, so if we knew either x or y, we could find the value of the other.

### Coefficient

Coefficients are used in a number of areas of mathematics, but in algebra, a coefficient is a factor that a term in an algebraic expression is multiplied by. From the example above:

x = 3y

The coefficient of 3 multiplies the variable y, telling us that x is 3 times of y. In the equation

x = 3y + 3

the second 3 is a constant, not a coefficient, though technically we can think of the 3 as 3x0, in which case 3 would be the coefficient of x0.