What defines a 'factor' in mathematics?

In mathematics, a 'factor' is defined as a number that, when multiplied by another number, yields a specific product. For instance, in the equation 3 × 4 = 12, both 3 and 4 are factors of 12 because their multiplication results in that product. This concept is fundamental in various mathematical operations, including multiplication and division, since knowing the factors helps in simplifying fractions, finding least common multiples, and solving equations.

The definitions provided in the other options do not accurately describe what a factor is. The first option refers to subtraction, while the third mentions a sum that yields an even result. These definitions are related to other mathematical operations rather than multiplication. The last option discusses a number that cannot be divided, which pertains to prime numbers but does not encapsulate the broader definition of a factor. Hence, the choice that conveys the accurate understanding of a factor is indeed the second one.