Basics on the topic 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 math because it helps to keep things organized when solving math problems or describing a math 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.
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.
Let’s look at the ordinal numbers in multiples of 10.
Hyphenated numbers keep the first word then use the ordinal version of the second number. Here are some examples of hyphenated ordinal numbers.
Ordinal Numbers – Example
Look at the picture below. What is the ordinal number for the kid in the green shirt?
- 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.
|What to do
| Find the person or object in a group to
which you want to assign an ordinal number to.
|Find the front or back of the line.
| Count from the front or the back to
your chosen person or object.
| Identify the number matching the
person’s or object’s position.
| 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 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 labeling 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 -st. Number two position is second, or a two followed by -nd. And three is third, or a three followed by -rd. The ordinal numbers from four to ten, except for five, end in -th, and sound like the regular number. Four is fourth, or four followed by -th. Five is fifth, where the -ve comes off and we add -fth. What about the number six? Six is sixth, or a six followed by -th. This pattern continues for seven, eight, nine, and ten! Multiples of ten up to one hundred use -th endings, or -ieth if they end in a 'y'. They also sound like their regular numbers. We already know ten, so we can look at the next multiple of ten, twenty. Twenty is twentieth, changing the 'y' to 'i' and add -eth. Thirty becomes thirtieth. Forty becomes fortieth. This pattern continues for fifty, sixty, seventy, eighty, ninety, and one hundred! Every other number in between multiples of ten except for numbers with one, two, three, or five in them have the -th added to the end of the number. Eleven is eleventh. What about the number thirteen? Thirteen is thirteenth. Thirty-six is thirty-sixth. Hyphenated regular numbers keep the first word, and the -th gets added to the last word! What about the number seventy-seven? Seventy-seven is seventy-seventh. Can you write twenty-one in ordinal form? Twenty one becomes twenty-first. Share any other ordinal numbers you can think of in the comments below! Now Skylar and Henry understand the position they finished and are ready to collect their medals, let's review! Remember, ordinal numbers describe the order of numbers. There are some different ways to write ordinal numbers. Numbers one, two, three, and five are special numbers. Multiples of ten up to one hundred have a -th ending, or -ieth if the number ends with a 'y'. Every other number in between these that do not have a one, two, or three in the number all end with -th. Ah, no wonder Skylar won the hopping contest, all thanks to her special frog suit. Cunning as always, Skylar!
Ordinal Numbers exercise
What are ordinal numbers?Hints
The 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.Solution
Ordinal numbers show the order or position of a number! First, second, and third are all examples of ordinal numbers.
Pair the ordinal and non-ordinal numbers.Hints
Remember, ordinal numbers are often just the cardinal number with a "-th" at the end of the number!
The ordinal numbers for one, two, three, and five don't follow the "-th" ending rule.Solution
Here are the matching numbers!
Match the ordinal numbers.Hints
Remember, 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.Solution
Here are the correct ordinal number pairs from this activity!
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?Hints
Hyphenated 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.Solution
All of these numbers use the normal "-th" rule to become ordinal numbers. Here are the correct numbers!
Which are the ordinal numbers?Hints
Remember, ordinal numbers are often just the cardinal number with a "-th" at the end of the number
Second is the ordinal version of two.Solution
Second, fourth, seventh, ninth, eleventh, fifteenth and seventeenth are all the ordinal numbers from this activity!
What are the ordinal numbers?Hints
Remember, 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
Here are a few more examples of ordinal numbers being written out!
All of these numbers didn't follow the "-th" rule in some way. Here are the correct ordinal numbers.