This is called a Trinomial because it consists of 3 terms. Constants ( “regular” whole number) and coefficients (number multiplying a variable) are both considered their own terms. A term is just an expression; it’s the relationship between a constant and a coefficient in an equation. For example: 5x-1. There are two terms in 5x-1; the two terms are 5x and -1. The relationship is that 5x is being subtracted by 1 (-1).