What are Ordinal Numbers?
Basics on the topic What are Ordinal Numbers?
Ordinal Numbers
What are ordinal numbers? When we are describing the order of objects we use ordinal numbers. Ordinal numbers are used to explain the position of something in a set. Ordinal numbers are used to show the order of things. This is useful in maths because it helps to keep things organised when solving maths problems or describing a maths solution.
What are ordinal numbers used for?
Think about the word ANSWER. The letter at the start of the word is A. That means it is the number 1 letter. When something is number 1 we say it is first. The letter N comes next. If we number the letters then the letter N is number 2.
A  N  S  W  E  R 

1  2  3  4  5  6 
When something is number 2 we say it is second. So N is the second letter in the word ANSWER. The S is number 3. When something is number 3 we say it is third. So S is the third letter in the word ANSWER. First, second and third are all ordinal numbers because they describe the order that the letters are in!
Ordinal Numbers – Spelling Rules
To make most ordinal numbers after 3 you just need to add a th to the end or ieth if the number ends in a y. For example, if you start with four and a th you now have fourth which is the ordinal form of four. If you start with twenty, remove the y and add ieth you now have twentieth. This method works for most ordinal numbers but there are exceptions. The v in the numbers five and twelve become f in their ordinal form so five becomes fifth and twelve becomes twelfth.
These are the ordinal numbers from 1 to 12.
cardinal number  ordinal number  short form 

one  first  1st 
two  second  2nd 
three  third  3rd 
four  fourth  4th 
five  fifth  5th 
six  sixth  6th 
seven  seventh  7th 
eight  eighth  8th 
nine  ninth  9th 
ten  tenth  10th 
eleven  eleventh  11th 
twelve  twelfth  12th 
Let’s look at the ordinal numbers in multiples of 10.
cardinal number  ordinal number  short form 

ten  tenth  10th 
twenty  twentieth  20th 
thirty  thirtieth  30th 
forty  fortieth  40th 
fifty  fiftieth  50th 
sixty  sixtieth  60th 
seventy  seventieth  70th 
eighty  eightieth  80th 
ninety  ninetieth  90th 
hundred  hundredth  100th 
Hyphenated numbers keep the first word then use the ordinal version of the second number. Here are some examples of hyphenated ordinal numbers.
cardinal number  ordinal number  short form 

thirtysix  thirtysixth  36th 
seventyseven  seventyseventh  77th 
twentyone  twentyfirst  21st 
fortythree  fortythird  43rd 
fiftyfour  fiftyfourth  54th 
Ordinal Numbers – Example
Look at the picture below. What is the ordinal number for the kid in the green shirt?
Remember:
 The first step is to find the kid in the green shirt.
 The second step is to find the front of the line. We can tell the start of the line is on the left because all of the students are facing left.
 The third step is to count from the front of the line to the kid in the green shirt.
 The fourth step is to identify that number as the answer.
The kid in the green shirt is fourth in line.
Ordinal Numbers – Summary
Ordinal numbers helped solve the problem and they helped to explain how to get to the answer. Ordinal numbers can be really useful! If you want to determine a position of someone or something within a group, you can use ordinal numbers to describe the order of a set. Let’s have a look at the steps to take in order to determine someone’s or something’s position in a group.
Step #  What to do 

1  Find the person or object in a group to which you want to assign an ordinal number to. 
2  Find the front or back of the line. 
3  Count from the front or the back to your chosen person or object. 
4  Identify the number matching the person’s or object’s position. 
5  Change the number to the number’s ordinal form by either adding th or using one of the special forms. 
You can use our interactive exercises and worksheets to practice using ordinal numbers.
Frequently Asked Questions Concerning Ordinal Numbers
Transcript What are Ordinal Numbers?
Skylar and Henry have taken part in a competition. They came first and third! However, Skylar and Henry do not know what this means. Let's join in and learn about ordinal numbers. When we say someone came first, fourth, or tenth in a race, we are labelling their position with ordinal numbers. Ordinal numbers describe the order, or position, of numbers. Ordinal numbers are written differently in number form and word form. Ordinal numbers for one, two and three are special. When something is in the number one position, this is first, or a one followed by
What are Ordinal Numbers? exercise

What are ordinal numbers?
HintsThe word ordinal gives you a clue to the purpose of ordinal numbers. What does the word ordinal sound like?
Ordinal numbers can be both even and odd.
First, second and third are all examples of ordinal numbers.
SolutionOrdinal numbers show the order or position of a number! First, second and third are all examples of ordinal numbers.

Pair the ordinal and nonordinal numbers.
HintsRemember, ordinal numbers are often just the cardinal number with a "th" at the end of the number!
The ordinal numbers for one, two and three don't follow the "th" ending rule.
SolutionHere are the matching numbers!
one: first
three: third
four: fourth
six: sixth
seven: seventh
ten: tenth

Match the ordinal numbers.
HintsRemember, some ordinal numbers are different and don't put a "th" at the end of the number.
One, two and three don't place a "th" at the end of the number to become ordinal numbers.
SolutionHere are the correct ordinal number pairs from this activity!
1st: first
2nd: second
3rd: third
4th: fourth
5th: fifth
The other ordinal numbers are incorrect. These added a "th" to the end of each number, but these numbers are different and don't follow that rule.

What are the ordinal numbers?
HintsHyphenated regular numbers keep the first word the same and the "th"gets added to the last word.
Adding a "th" to the end of most numbers makes them ordinal numbers.
SolutionAll of these numbers use the normal "th" rule to become ordinal numbers. Here are the correct numbers!
21: twentyfirst
18: eighteenth
26: twentysixth
33: thirtythird
10: tenth

Which are the ordinal numbers?
HintsRemember, ordinal numbers are often just the cardinal number with a "th" at the end of the number
Second is the ordinal version of two.
SolutionSecond, fourth, seventh, ninth, eleventh, fifteenth and seventeenth are all the ordinal numbers from this activity!

What are the ordinal numbers?
HintsRemember, numbers that normally end in a "y" will have an "ieth" ending as an ordinal number.
Hyphenated regular numbers keep the first word the same and the "th"gets added to the last word
Look at these examples of ordinal numbers being written out.
7: seventh
15: fifteenth
SolutionAll of these numbers didn't follow the "th" rule in some way. Here are the correct ordinal numbers.
1: first
2: second
3: third
5: fifth
13: thirteenth
30: thirtieth
52: fiftysecond