# Correct usage of 'Coefficient'

If I have a equation like $f(x) = ax^2 + bx + c$ then $a$ and $b$ can be called the coefficients. Is it correct to refer $x$ as a coefficient as well?

e.g.

If I have $ax + by + cz$ then can I call all of $a$, $b$, $c$, $x$, $y$ and $z$ coefficients?

No: $a$, $b$, and $c$ are the coefficients of the terms $ax$, $by$, and $cz$, respectively, since $a$, $b$, and $c$ are (real) numbers. We refer to $x$, $y$, and $y$ as variables (their values change and are taken to be real numbers, whereas $a$, $b$, and $c$ remain the same).
• @banksysan $x$ is a variable, not a coefficient. – Mark S. Apr 4 '17 at 22:40