ETYM Latin factor a doer: cf. French facteur a factor. Related to Fact.
1. Any of the numbers (or symbols) that form a product when multiplied together.
2. Anything that contributes causally to a result.
In mathematics, an item that is multiplied in a multiplication problem; for example, 2 and 3 are factors in the problem 2 x 3. The prime factors of a number are a set of prime numbers that, when multiplied together, produce the number.
A number that divides into another number exactly. For example, the factors of 64 are 1, 2, 4, 8, 16, 32, and 64. In algebra, certain kinds of polynomials (expressions consisting of several or many terms) can be factorized. For example, the factors of x2 + 3x + 2 are x + 1 and x + 2, since x2 + 3x + 2 = (x + 1)(x + 2). This is called factorization. See also prime number.

To resolve into factors; SYN. factor in, factor out.