Definition
Odd number
An odd number is an integer that is one more than a multiple of 2.
What it means
Make pairs. If exactly one item is left without a partner, the number is odd. In base ten, an integer ending in 1, 3, 5, 7, or 9 is odd.
Remember it
Make pairs; one waits alone.
Example
Arrange 27 counters into pairs. They make 13 pairs with one counter left, so 27 is odd; algebraically, 27 = 2 × 13 + 1.
Watch for
Zero is not odd; it makes zero complete pairs with nothing left.
Common mix-up
In mathematics, odd names this number property; it does not mean strange or unusual.
Exact meaning
An odd number is an integer of the form 2 × k + 1 for some integer k. Equivalently, it is an integer that is not divisible by 2.