Ordinal Numbers (1st through 10th) - First Grade Mathematics
Numbers have two major jobs in our world. Their first job is to tell how many items there are in a group (like "5 ducks" or "10 crayons"). These are called cardinal numbers. But numbers also have a second, equally important job: to tell the position or order of an object in a line (like who is first in line for lunch, or what floor of an apartment building you live on). These special position words are called ordinal numbers. In this chapter, you will learn the names, abbreviations, and positions for ordinal numbers from 1st through 10th.
The Ordinal Sequence from 1st to 10th
When objects are lined up, each position has its own unique ordinal name and abbreviation.
The Line-Up from Left to Right (Moving toward the Flag):
(*) (*) (*) (*) (*) (*) (*) (*) (*) (*) |FLAG|
10th 9th 8th 7th 6th 5th 4th 3rd 2nd 1st
tenth ninth eighth seventh sixth fifth fourth third second first
Words and Short-Form Abbreviations
Every ordinal number can be written as a full word or as a short numeral with two small letters attached to the end: First is written as 1st (ends with "st"). Second is written as 2nd (ends with "nd"). Third is written as 3rd (ends with "rd"). Fourth through tenth all end with the sound "th": 4th, 5th, 6th, 7th, 8th, 9th, and 10th.
Notice the Special Spellings
Notice that some ordinal words change their spelling slightly from their cardinal number names: "One" becomes first, and "two" becomes second. "Three" becomes third, and "five" changes to fifth (not five-th). "Eight" adds only an "h" to become eighth (not eight-th). "Nine" drops the "e" to become ninth (not nine-th).
Finding Position Depends on the Starting Point
To name an object's ordinal position correctly, you must always know which direction the line is moving and where the line begins.
Runner Race: Who is in Which Place?
[Finish Line] <--- [Runner A] [Runner B] [Runner C] [Runner D]
1st 2nd 3rd 4th
(first) (second) (third) (fourth)
The Leader of the Line
In a race, the runner closest to the finish line is in 1st place. The runner right behind them is in 2nd place, followed by 3rd place and 4th place.
Checking Which End Is "First"
Always ask: "Where does the line start?" If a line of ducklings is following a mother duck who is walking to the left, the duckling closest to the mother is first. If the mother turns around and walks to the right, the position counts from the other side!
Ordinal Numbers in Everyday Life
You use ordinal numbers every day without even realizing it.
Everyday Examples of Ordinal Numbers:
- Calendar Dates: "Today is October 1st."
- Building Floors: "She lives on the 3rd floor."
- School Grades: "Welcome to 1st grade!"
- Birthdays: "Happy 7th birthday!"
- Books and Chapters: "Turn to the 2nd chapter."
Following Multi-Step Directions
Ordinal words help you follow instructions in exact order: "First, wash your hands. Second, dry them with a towel. Third, sit down to eat." Doing things in the correct order keeps your day organized and safe.
Practice Exercises
Exercise 1: Write down the ordinal abbreviations for these position words: first, third, second, fifth, eighth, and tenth.
Exercise 2: Five toy cars are lined up in a race facing the finish line: a red car, a blue car, a green car, a yellow car, and an orange car. The red car is closest to the finish line, followed in order by blue, green, yellow, and orange. In what ordinal position is the green car? In what position is the orange car?
Exercise 3: Name the special ending letters used on the abbreviations for 1st, 2nd, and 3rd. What ending letters are used for 4th through 10th?
Exercise 4: Look at this row of shapes from left to right: Square, Circle, Triangle, Star, Heart. Which shape is 2nd from the left? Which shape is 4th from the left?
Solutions and Explanations
Solution to Exercise 1: First is 1st. Third is 3rd. Second is 2nd. Fifth is 5th. Eighth is 8th. Tenth is 10th.
Solution to Exercise 2: Since red is 1st and blue is 2nd, the green car is in 3rd place (third). The yellow car is 4th, which makes the orange car in 5th place (fifth).
Solution to Exercise 3: The abbreviation for 1st ends with "st" (from fir-st). The abbreviation for 2nd ends with "nd" (from seco-nd). The abbreviation for 3rd ends with "rd" (from thi-rd). For 4th through 10th, all abbreviations end with "th" (fourth, fifth, sixth, seventh, eighth, ninth, tenth).
Solution to Exercise 4: Counting positions from left to right: the Square is 1st, the Circle is 2nd, the Triangle is 3rd, the Star is 4th, and the Heart is 5th. Therefore, the shape that is 2nd from the left is the Circle, and the shape that is 4th from the left is the Star.