Cardinal and ordinal numbers can get tricky. It’s a common mistake for my students to say “the number five question,” instead of “the fifth question.” A lot of my students tend to rely on their knowledge of cardinal numbers only, but ordinal numbers are just as important to know.
Cardinal numbers tell ‘how many’ of something, they show quantity. Ordinal numbers tell the order of how things are set, they show the position or the rank of something.
I’m sure you know how to use cardinal numbers! How many eyes do you have? You have ‘two’ eyes. We use cardinal numbers for counting (think cardinal = counting).
Ordinal numbers all use a suffix. The suffixes are: -nd, -rd, -st, or -th. Examples: ‘second’ (2nd), ‘third’ (3rd), ‘first’ (1st), and ‘tenth’ (10th). We use ordinal numbers for dates and the order of something (think ordinal = order).
‘January 15, 2013’. If we were to say this date it would be: ‘January fifteenth, twenty-thirteen’.
‘List of students: John, Mary, Henry, Ron, Sally, Jeff, and Robert.’
Where is Henry in line? Henry is third in line.
Who is fifth in line? Sally is fifth in line.
I hope this helps with distinguishing the difference between cardinal and ordinal numbers. When in doubt try to remember C = cardinal counting and O = ordinal ordering (dates are used to order days… right?). Practice makes perfect, I know you can do it!