Question

What is a coefficient?

Answer 1

"A number used to multiply a variable.
Example: 6z means 6 times z, and "z" is a variable, so 6 is a coefficient.

Variables with no number have a coefficient of 1.
Example: x is really 1x.

Sometimes a letter stands in for the number. 
Example: In ax2 + bx + c, "x" is a variable, and "a" and "b" are coefficients."

hope this helps you!