Mean - the sum of all the numbers in a sample or population, divided by the number of elements in that sample or population. Also called the average.

Median - If all elements in a sample are arranged from lowest to highest, the middle number. Also called the 50th percentile.

Mode - The number that occurs most frequently in a sample. If no number appears more than once, there is no mode.

In a perfectly distributed normal population, the mean, median, and mode are all equal.

Range - The largest number in a sample, minus the smallest.

Numerator - the top number in a fraction. The 3 in 3/4.

Denominator - the bottom number in a fraction. The 4 in 3/4.