When getting back to math-based questions after it’s been a while since math class, many of us need a refresher on some key terms that are used and what they mean. Here are five that you’re likely to come across and a quick definition to refresh your memory.

1. Integer- Probably the most commonly used number term, integer is a commonly confused term. I like to say that if you were going to draw a number line, an integer is anywhere you would draw a dash, including zero and negatives. So, -2, -1, 0, 1, 2, and 3 are all integers, while 1.4 and 2/3 are not.

2. Whole Number- While this term isn’t commonly used in tests, it’s one you’ve heard before and it can easily be confused with the term integer. While there is a great deal of overlap between the two groups, the group of whole numbers does not include negative numbers. So, while 0, 1 and 2 are both integers, -3 is an integer but not a whole number.

3. Multiple- A number is a multiple of another number– for instance 8– if it is the product of that number and an integer. So, 24 is a multiple of 8 because 24= 8 * 3 and 3 is an integer. Similarly, 0 and -16 are multiples of 8 because they are the product of 8 and an integer (8 * 0 = 0, 8 * -2 = -16). 4 is not a multiple of 8 because it is the product of 8 and a non-integer (8 * 0.5 = 4).

4. Factor- A factors are the integers you multiply together to get a number. They come in pairs. For instance, if we were factoring 18 we would see that 6 * 3 = 18, so both 6 and 3 are factors. So are 9 and 2, and 18 and 1. Factors can be negative as well, although that is rarely tested.

5. Prime Numbers- A prime number is a number whose positive factors are only 1 and itself. Since no integers other than 1 and 13 divide evenly into 13, it is prime. Common misconceptions about prime numbers are than 1 is prime (it isn’t), and that all prime numbers are odd (2 is a prime number).

Hopefully that served as a good refresher!