in Algebra, are such numbers or known quantities as are put before letters or quantities, whether known or unknown, and into which they are supposed to be multiplied. Thus in $3x$, $ax$, or $b \cdot x$; $3$, $a$, and $b$, are the coefficients of $x$; and in $6a$, $9b$; $6$ and $9$ are the coefficients of $a$ and $b$. See Algebra.