Number where the ones digit is 1, 3, 5, 7 or 9.

- Number that is a multiple of 2 minus one.
- Number in the form (2
*n*+ 1) or (2*n*– 1) where*n*∈ \(\mathbb{Z}\).

### Examples

- The sequence of odd whole numbers is: {1, 3, 5, 7, 9, 11, 13, …}.
- The set of odd integers is : {…, –7, –5, –3, –1, 1, 3, 5, 7, …}.
- Numbers like 4.5 or -12.9 are not odd numbers, because they are not integers.