Ordinals

In this lesson, we will learn:

• How to write ordinal numbers using numbers and superscripts
• How to write ordinal numbers using words and suffixes
• How to use ordinal numbers to understand order/ranking/position

Notes:

• Ordinal means Order
• Ordinal numbers answer the question “what place/rank/position”?
• Ordinal numbers are whole numbers only (no fractions nor decimals)


• Ordinal numbers follow similar rules to the way we write number word names
• The difference is that ordinals have special endings, or “suffixes”
• When you write ordinals as numbers, these endings are superscripts
• You write these letters smaller and write them above the normal line
• i.e. 1^st, 2^nd, 3^rd, 4^th, 5^th, 6^th, 7^th, etc.
• When you write ordinals as words, most ordinal numbers end with “–th” except for numbers that end with 1, 2, or 3 (which use “–st”, “–nd”, and “–rd”, respectively)
• For multiples of ten from 20 to 90, they end with “–ieth”
• The ordinal 9^th is spelled as “ninth” without the e (that is usually in nine)

• There are 3 types of numbers: Cardinal, Ordinal, and Nominal
• Cardinal means Counting (ex. there are 6 pool balls)
• Ordinal means Order (ex. the purple pool ball is in 4^th place)
• Nominal means Name (ex. the green pool ball is labelled “14”)


• It’s important to know the difference between the word names for written ordinal numbers, written decimals, and written fractions:
• Ex. 200^th is written as two hundredth
• Ex. $\frac{2}{100}$ is written as two-hundredths
• Ex. 0.02 is written as two hundredths