Purpose

By the end of this lesson, you will be able to say and correctly spell the numbers from 0 to 100, form compound numbers like 21 and 47 correctly, and know which common number spellings are frequently mistaken.

Lesson Explanation

The numbers from 0 to 12 each have their own individual word, and must be memorized directly, since they do not follow a predictable pattern:

0 zero      5 five      10 ten
1 one       6 six       11 eleven
2 two       7 seven     12 twelve
3 three     8 eight
4 four      9 nine

The numbers 13 to 19 are formed by adding -teen to a root, though several have a genuinely irregular spelling worth noting specifically:

13 thirteen   14 fourteen   15 fifteen   16 sixteen
17 seventeen  18 eighteen   19 nineteen

Notice thirteen and fifteen change the root spelling (three→thir-, five→fif-), unlike fourteen or sixteen, which keep the root unchanged.

The tens from 20 to 90 also have their own specific words:

20 twenty   30 thirty   40 forty   50 fifty
60 sixty    70 seventy  80 eighty  90 ninety

Notice specifically that forty drops the “u” that appears in “four” — this is a genuinely common spelling mistake, since people often write “fourty” by analogy with “four,” but the correct spelling has no “u.”

Numbers between the tens (like 21, 47, 99) are written as the tens word, a hyphen, and the ones word: twenty-one, forty-seven, ninety-nine. The hyphen is a required part of correct spelling for these compound numbers.

The number 100 is one hundred (or simply a hundred in casual speech).

Practice Questions