-tio

• -siō (in primarily third conjugation verbs with stems ending in -t-, -d-, -rg-, -ll-, or -rr-.)
• -ciō (Medieval Latin)

Probably from Proto-Italic *-tjō, an n-stem extension of Proto-Indo-European *-tis.

Alternatively, from Proto-Indo-European *-Hō or from Proto-Indo-European *-tyon with Old Armenian -ութիւն (-utʻiwn) as a cognate. (Can this⁽⁺⁾ etymology be sourced?)

• (Classical Latin) IPA^(key): [ti.oː]
• (modern Italianate Ecclesiastical) IPA^(key): [t̪͡s̪i.o] (stressed on the antepenult)

-tiō f (genitive -tiōnis); third declension

1. -tion, -ation, -ing; suffixed to verbs to form action nouns denoting a process, action, or result of an action.

   dictātiō (“a dictating, dictation”) ← dictō, dictātum (“to dictate”)

   quadripartītiō (“a division into four parts”) ← quadripartiō, quadripartītum (“to divide into four parts”)

• For informations concerning word formation using this suffix, see usages notes at -tus.
• The suffix is occasionally added to other parts of speech, or appears in situations where no related verb apparently exists; more at -ātiō.

gradātiō (“making of a staircase or steps”), from gradus (“step, pace”).

Third-declension noun.

• -tūra, -tus

• -ātiō
• -itiō
• -ītiō

• Haudry, Jean (1981) L'indo-européen, pages 55-56
• Sihler, Andrew L. (1995) New Comparative Grammar of Greek and Latin, Oxford, New York: Oxford University Press, →ISBN