Just a rule of thumb from my perspective (compound words are not included), such as th/t/s/z/c + /V/ + n/m:


-tion/-sion (question, division, conclusion),


-than (leviathan),

-thon (marathon, python),

-thm (algorithm, rhythm),

-thom (fathom),

-them (anthem),


-sm (apriorism, prism),

-san (artisan, courtesan, partisan, ptisan),

-son(bison, prison, season),

-som(blossom, bosom, ransom, transom),


-zan (azan, bartizan),

-zen (citizen, dozen),

-zam (Nizam),

-zem (chernozem, diltiazem),

-zon(horizon, Amazon, menazon, blazon, cabezon),


-can (florican, pecan, pelican, toucan),

-cam (piroxicam).


English words in -tion/-sion are nouns because this suffix comes from Latin, where it was a productive way of forming action nouns. Some of these English nouns are borrowings directly from Latin, but this suffix has become productive in English too. (Some nouns on your list are from the same origin but borrowed through French, with a change in spelling and pronunciation, e.g. benison.)

The class of words in -ism (and less frequently in -asm and -thm) comes from Greek, where -smos was a productive abstract noun formant. In this case too, -ism has become productive in English, so many words with this suffix don't have a Greek source (e.g. capitalism).

Other than these two classes, I don't think there's really a pattern here; many of the other nouns you list are very rare, and I'm sure one could come up with a few verbs with similar endings to balance them.

  • 1
    -thon is also a productive suffix now. Very few of your words with -z- are common, and several of them are arguably not English. – Colin Fine Oct 8 '13 at 13:17

This is because the Proto-Indo-European language from which English derives had the ending -om in nominative for inanimate(neuter) nouns. Some words and suffixes were borrowed into English from Latin and Greek who also derived from PIE.

Other words derive from PIE words ending with -m-os and -n-os (which was a common derivational construction) with the ending -os later disappearing.

The words derived from non-IE language were often anglicized, latinized or hellenized before entering English.

For example, the -tion suffix comes from Latin, where it is inherited directly from PIE -ti̯om. It is a common combination of suffixes plus nominative ending of neuter/inanimate gender. Some examples of the reconstructed PIE words with that suffix:

a̯usti̯om river mouth

plea̯ti̯om a kind of dress (cloak)

tra̯nsprtea̯ti̯om act of carrying across

Leviathan is just a borrowing from Hebrew with little change.

Python and Marathon are borrowings from Greek where -on is the nominative ending directly derived from PIE nominative ending -om.

The suffix -ism is derived from PIE adjective suffix combination+ending -ismos

  • As far as I can see, none of the words in the poster's list go back to PIE neuters in *-om. Latin -tion- is not a neuter suffix and isn't from *-om, and neither are the Greek words cited, which are animate nouns in -ōn. – TKR Oct 8 '13 at 4:33
  • @TKR Latin -tion directly comes to PIE -ti̯om – Anixx Oct 8 '13 at 4:34
  • 1
    Latin action nouns in -tiōn- are feminine n-stems, and have nothing to do with neuter o-stems (PIE nom./acc. sg. *-om). PIE *-om gives Latin -um. – TKR Oct 8 '13 at 4:45
  • 1
    @Anixx You're still connecting two unrelated things; there's no way an animate n-stem can come from a neuter o-stem, especially when the latter class already has an obvious reflex in Latin. The -m of *-o-m is a case ending so has nothing to do with the -n- of -tiōn-, even if there was some sound change that could connect them. Latin -tiōn- appears to be built of the feminine abstract noun suffix -ti- (cf. Gk. mētis etc.) plus the same -ōn- of Gk. marathōn, pythōn etc. (The latter also has an e-grade form, e.g. Gk. Hellēn, which maybe is what you mean by the "mysterious suffix -i̯en-"?) – TKR Oct 8 '13 at 17:27
  • 1
    @Anixx -ōn is still fairly productive in Greek for forming names, adjectives, etc. - see Chantraine's Formation du nom en grec ancien for examples. In any case the point for this question is that PIE *-om > Lat. -um, Gk. -on, so the suffix -(ti)ōn- in either language has no relevance here. – TKR Oct 9 '13 at 16:59

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