Cardinals and Ordinals
As a child, I learned about cardinal and ordinal numbers. I just checked Wikipedia and found that my understanding of them is … childlike. I remember cardinal numbers as non-negative integers; 0, 1, 2, 3, and so on. I remember ordinal numbers as first, second, third, and so on.
The difference is as follows. Suppose we have ten numbers listed from smallest to largest; 2, 3, 5, 7, 11, 13, 17, 19, 23, 29. (Can you guess how I chose them?) The first number is 2. The second number is 3. The ninth number is 23.