In mathematics, parity is the property of an integer of whether it is even or odd. An integer's parity is even if it is divisible by two with no remainders left, and its parity is odd if it isn't; that is, its remainder is 1. Odd numbers are whole numbers that cannot be divided exactly into pairs. Odd numbers, when divided by 2, leave a remainder of 1. 

Fun facts: the sum of two odd numbers is always even; the product of two or more odd numbers is always odd; the sum of an even number of odd numbers is even, while the sum of an odd number of odd numbers is odd.