Need a refresher on odd and even numbers? Technically, an odd number is any integer that cannot be divided exactly by 2. An even number is any integer that can be divided exactly by 2. This obviously doesn't make much sense to a second grader, so again we use simpler words in math class - still keeping with as much math vocabulary as possible.
An odd number, when placed into pairs, will always have one left over. The number of items will not be able to be placed into equal groups. In the picture below, the students are placed into two groups. Any way you group the students, there will be one student left over.
An even number can be placed into matching pairs or the number of items can be divided into an equal number of groups. The kids below are in two equal groups of five.
Check out these great games!
Paint by numbers pictures.
Circle diagram odd and even number sorting:
Labeling numbers as odd or even: