Cum is a common preposition meaning "with" (as in "accompanying", not "using"). For example, if Caesar returned to Rome with his soldiers, that would be cum militibus suis. As a preposition, it comes before what it modifies: *militibus suis cum sounds distinctly odd to me.


When it's combined with a personal pronoun, everything seems to go backwards. Instead of cum me "with me", we see me-cum; similarly, te-cum "with you", nobis-cum "with us", vobis-cum "with all of you".

Why does this happen? It seems to be peculiar to cum: we don't see *me-ob for "because of me", for example.

(Related: this question discusses when this happens, but I'm interested in why.)

3 Answers 3


Postpositive cum is rather unique in Latin in this regard (but not for PIE - see below), although there are some other postpositive uses found in Latin; they are well-known, e.g. Leumann mentions quo-ad (cf. ad-huc or ad-eo), see Fortson 2010b: 136 for more examples.

Basically, there are two approaches - either postpositive cum is an archaic holdover (communis opinio for decades - e.g. Clackson 2004 or s.v. com-, con-, co-; cum in de Vaan) or innovation (a new approach proposed, for instance, in Fortson 2010b).

After all, we usually don't reconstruct prepositions for PIE (see any textbook on PIE or historical linguistics, e.g. Beekes 2011: 245 or Fortson 2010a: 154, section 8.8), so it is quite common to trace IE prepositions back to PIE adverbs.

cf. Ivanov 1999 "It can be suggested that the Indo-European particle/adverbial element *kom could be used both as an enclitic or as a proclitic"


Fortson 2010a "From the comparative evidence it is not entirely clear whether these forms were prepositions, or rather occurred after their objects as postpositions; probably both patterns were current, though many researchers assume postpositional usage to be older. [...] In the other older IE languages [i.e. not Anatolian or Vedic - Alex B.], prepositions are the rule, although some (e.g. Old Persian, Greek, and Latin) evince limited postpositional use, like [...] Latin mecum."

Baldi 2017 explains this very clearly. When such particles (adpositions) combine with nomimals in PIE, they follow the noun they modify, whereas when they combine with verbs, they precede the modifying verb (p. 814). He also argues that data from other Italic languages (e.g. Umbrian), combined with Latin and Oscan data, "provide significant evidence for postpositional Proto-Italic" (p. 814).

see my other post

Since there are some prepositions in Latin that don't behave quite like typical prepositions, Weiss prefers to talk about adpositions instead (e.g. pp. 460-461).

NB: Weiss also adds that "[p]ostposition after pronominals is common with disyllabic forms like inter, propter, contra, etc." (footnote 45, p. 460).


This is a cross-linguistic phenomenon: pronouns, especially if they cliticise, can have a different syntax from the nouns they replace.

For a very nearly parallel example, consider Germanic compounds, not with personal but with anaphoric pronouns: English therewith, German damit.

For a different example, consider French object pronouns: they have enclitic forms which precede the verb, unlike other object NPs: Je te vois vs. Je vois la maison.

  • 1
    Very interesting! But in English you also see therein, thereby, etc, and German dafür and so on. This seems different, because it happens only with cum, not with other prepositions.
    – Draconis
    Commented Jan 26, 2019 at 0:20
  • Also Welsh and Irish pronouns form sometimes opaque compounds with prepositions, eg W gan fi -> gennyf ("with me"). But again, that is not restricted to "with". I haven't an answer to "why only cum". But "Why" questions about language hardly ever have substantive answers.
    – Colin Fine
    Commented Jan 26, 2019 at 14:10

In Orator Cicero writes:

Quid, illud non olet unde sit, quod dicitur cum illis, cum autem nobis non dicitur, sed nobiscum? Quia si ita diceretur, obscaenius concurrerent litterae, ut etiam modo, nisi autem interposuissem, concurrissent. Ex eo est mecum et tecum, non cum me et cum te, ut esset simile illis nobiscum atque vobiscum.

To paraphrase, the Romans did not say cum nobis but nobiscum, because otherwise the letters would coincide obscenely, forming the word cunnus. Then the other pronouns get their cum at the end by analogy.

I am not claiming that this is what necessarily happened, but that this is the rationalisation a notable Roman gave. I would be glad to know whether Cicero got it right.

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    I had the impression that this was more of an after-the-fact explanation, not the original reason for this word order
    – Asteroides
    Commented Jan 25, 2019 at 23:21
  • I'm sure this is a rationalisation. See my answer.
    – Colin Fine
    Commented Jan 26, 2019 at 0:16
  • @sumelic Quite possibly so. I expanded my answer to elaborate on my position.
    – Joonas Ilmavirta
    Commented Jan 26, 2019 at 12:19

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