Unit 8.1

Cardinal numbers: Tens


Cardinal numbers give information about how many people or things there are.

Ten numbers go from 1 to 99.


Ten numbers have ten as its base. However, the numbers from 1 to 9 are commonly called unities.

They have specific features:

  • plain form: number + 0
  • specific names from 0 to 20
  • from 20 to 99 the numbers follow a pattern to name them: using a hyphen in between the ten number and the unit.
Unities from 1 to 9 Tens from 11 to 19 Tens from 10 to 90 Tens + unities
one eleven ten twenty-one
two twelve twenty twenty-two
three thirteen thirty twenty-three
four fourteen fourty twenty-four
five fifteen fifty twenty-five
six sixteen sixty twenty-six
seven seventeen seventy twenty-seven
eight eighteen eighty twenty-eight
nine nineteen ninety twenty-nine

NOTE: We normally use the singular form of the numbers when we are naming a concrete figure, while we use the plural form when we are not speaking about a concrete number, but in general terms.


  • 10 (ten)
  • 25 (twenty-five)


Tens numbers are used to measure, count, label things, codes from 1 to 99.

In formal writing it is better to write the number in letters when it is a short figure.


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