Ordinal Numbers
Ordinal numbers describe position or order — first, second, third — and are abbreviated as 1st, 2nd, 3rd, 4th, and so on. Unlike cardinal numbers that count quantity, ordinal numbers tell where something falls in a sequence. May is the 5th month; the 4th person in a line of ten is Pedro. This concept is part of Saxon Math Intermediate 4 and is a practical 4th grade math skill that students use constantly in calendars, rankings, sequences, and everyday language.
Key Concepts
Property Numbers that tell position or order, like first, second, or third. They are abbreviated with a number and letters like 1st, 2nd, and 3rd.
Examples Example: If ten people are in line, the 4th person is Pedro. Example: The month of May is the 5th month of the year. Example: The final contestant was the 12th person to audition for the show.
Explanation Think of a race! Ordinal numbers don’t just count the runners; they tell you who won, like who came in 1st place. They answer the question “which one?” not “how many?” It's the secret to knowing your exact spot in any lineup or sequence.
Common Questions
What are ordinal numbers?
Ordinal numbers describe the position of something in a sequence: first (1st), second (2nd), third (3rd), fourth (4th), and so on. They answer the question 'Which one?' rather than 'How many?'
What is the difference between cardinal and ordinal numbers?
Cardinal numbers count quantity: one, two, three. Ordinal numbers describe position: first, second, third. So 'five students' uses a cardinal number, while 'the fifth student' uses an ordinal.
How do you abbreviate ordinal numbers?
Write the digit followed by the suffix: 1st, 2nd, 3rd, 4th, 5th, 6th... The suffixes st, nd, rd, th follow the spoken form. From 4th onward, th is used for all numbers except those ending in 1, 2, or 3.
When do students learn ordinal numbers?
Ordinal numbers are introduced in kindergarten and reinforced through elementary school. Saxon Math Intermediate 4 uses ordinal numbers in calendar work, problem-solving sequences, and positional reasoning in 4th grade.
What are examples of ordinal numbers in real life?
Ordinal numbers appear everywhere: the 3rd floor of a building, finishing 2nd in a race, the 12th month of the year (December), the 1st day of school, or a player ranked 7th on a leaderboard.
What are common mistakes with ordinal number abbreviations?
Students sometimes write '2st' or '3nd' instead of '2nd' and '3rd.' The rule: 1st, 2nd, 3rd, then th for all others — unless the number ends in 11, 12, or 13, which always use th (11th, 12th, 13th).