The factor of primary school is the prime number obtained when the composite number is decomposed.

The factor of middle school is a formula obtained by factorization.

University factor is one of the methods to solve ordinary differential equations, which requires partial derivatives of functions.

The factor of an integer is an integer divisible by it. However, we generally consider positive integers. For example, the factor of 8 is 1, 2, 4, 8. If you remove this integer, it is a real factor.