An odd number is an integer that is not even. In other words, odd numbers are integers not divisible by 2, like the following numbers. -5, -3, -1, 1, 3, 5 ... All these numbers are not multiples of 2 and result in a not integer rational number when divided by 2.

n	n/2	n/2=k	Odd?
-5	-5/2	- 2.5	Yes
- 3	- 3/2	- 1.5	Yes
- 1	- 1/2	- 0.5	Yes
1	1/2	0.5	Yes
3	3/2	1.5	Yes
5	5/2	2.5	Yes

Odd numbers are usually defined as all numbers n that can be written in the form n=2k+1, where k is an integer.