A numerator is the top number in a fraction. A denominator is the bottom number. The line between them can be vertical or horizontal.
The numerator shows how many parts there are, while the denominator shows how many parts make up the whole. The numerator can be bigger than the denominator, but fractions with a value of more than one are “wrong.” When the numerator is bigger than the denominator, the fraction needs to be broken down even more.
In a fraction, the denominator can never be 0. But a numerator can be zero, and the calculation will still come out to be zero.