Often, the terms "linear equation" and "linear function" are confused. Both are polynomials. However, the word "linear" in "linear equation" means that all terms with variables are first degree. (The word "linear" in "linear function" means the graph is a line.) A linear equation can have 1, 2, 3, or more variables. So a linear equation is a linear function only if it has exactly 2 variables. (A linear equation in one variable is a point on the number line and a linear equation in 3 variables is a plane in 3-dimensional space.)