Begin by introducing the vocabulary word even. Line up counters side by side in pairs to create a double line of 2, 4, 6 or 8 things.
Tell students that as long as each counter is in a pair, the number of counters is even. For younger students, tell them that as long as each counter has a partner, it's even. For example, two counters paired together side by side means the number two is even.
Isolate four counters paired together side by side to show them that four is an even number. Continue the process for six and eight.
Note by writing on the board that 2, 4, 6 and 8 are always even numbers at the end of the process. Tell students that 0 is also an even number because when it's divided by 2, there isn't a remainder. For younger students, tell students 0 is even because it follows the pattern when counting even numbers on a number line or a hundred chart.
Tell students when counters are not in pairs, the number of the counter is odd. For younger students, tell them that if the object doesn't have a partner the number is odd.
Isolate one counter. Tell students that since the counter is not in a pair, one is an odd number.
Pair two counters side by side and one counter behind either counter. Tell students since one counter is not in a pair then the number three has to be an odd number. Continue the process for 5, 7 and 9.
Write on the board that 1, 3, 5, 7 and 9 are always odd numbers.
As students begin to understand, test them by writing a number on the board and having volunteers say "odd" or "even."