Learn English – Are there any solid reasons for the “-st”, “-nd”, “-rd”, and “-th” suffixes for numbers

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Is there any reason why we say 1st, 2nd, 3rd and the rest (4, 5,.. 10,..) are all -th except the one ending in 1, 2, 3? Why does it change specifically for 1, 2, 3?

Best Answer

Historical accident.

  • First derives from the same root as fore, before, in the superlative grade—it meant, originally, “fore-est”, that is ‘foremost’.
  • Second derives from Latin secundus, originally a participial form of sequor meaning ‘following’

All the others derive from a common Proto-Indo-European ending -tos, which in Old English was variously realized, depending on dialect and on phonological context, as -þe (þ = {th}, voiced or unvoiced), -te or -de, before it lost its ending somewhere around the transition from Middle English to Early Modern English and settled on -th. The alternate ending -t (‘fourt’, ‘fift’, ‘sixt‘, &c) is still to be heard in many dialects.

  • Third, however, which was regularly thridde or thrydde, started transposing the -rid- to -ird- in 10th-century Northumbria, and in the course of the next four centuries this established itself as the preferred pronunciation. Why? Who knows? But the same thing happened to bird, which was originally bryd.
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