Forty Number Names
English builds every number from a small kit of roots, two suffixes and three scale words — and the kit shows its seams.
English number names are built from a small kit. The atoms are the words one to ten; the scale words are hundred, thousand and million; and two suffixes, -teen and -ty, cover everything between. Any number in the language can be assembled from these parts.
The teens mean unit and ten: thirteen is three and ten, nineteen is nine and ten. Eleven and twelve stand outside the pattern — they descend from old words for one left and two left after ten, which is why they share no visible root with one and two.
The decades mean unit times ten, using a suffix that is itself a worn-down relative of the word ten. The joins are mostly smooth, but four roots adjust their shape: two becomes twen- in twenty, three becomes thir- in thirty, five becomes fif- in fifty, and four loses its u in forty.
Between the decades, English stacks decade and unit with a hyphen: forty-one, ninety-nine. Hundreds and thousands sit in front as multipliers — three hundred, four thousand — and British English adds and before the final stretch: three hundred and forty-five.
Ordinals mostly add -th: fourth, tenth, hundredth. A handful resist: first, second, third, fifth, eighth, ninth, twelfth. Fortieth follows its cardinal exactly — the u stays missing, and only the ending changes.
Further reading