# Coefficient

The English Wiktionary has a dictionary definition (meanings of a word) for: coefficient

In mathematics, a coefficient is a constant multiplicative factor of a certain object. For example, the coefficient in 9x2 is 9.

The object can be such things as a variable, a vector, a function, etc. In some cases, the objects and the coefficients are indexed in the same way, leading to expressions such as:

$a_1 x_1 + a_2 x_2 + a_3 x_3 + \cdots$

where an is the coefficient of the variable xn for each n = 1, 2, 3, …