Before a consonant on can use either version of the prepositions e/ex. Both seem to appear in prefixes as well, but ex- is often assimilated. It seems that, for example, words beginning with F take ex-: efficere, efferre, effundere… On the other hand, words beginning with L take e-: eligere, elevare, eloqui… My examples are verbs, but the pattern does not seem to be restricted to them.

This little observation suggests that some consonants (like L) require the prefix e- while others (like F) require ex-. Which ones take e- and which ones ex-? Are there perhaps consonants that can take either one? Is there an easy way to memorize or understand the division to two consonant types?

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    Related question about the prepositions rather than the prefixes: Why “ex nihilo” instead of “e nihilo”?
    – Asteroides
    Commented Jan 23, 2017 at 23:20
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    I suspect it has to do with whether the consonant following is voiced or unvoiced (we have enervo, emendo, egredior but exsorbeo, expendo, extero). Commented Feb 2, 2017 at 18:02
  • @JoelDerfner Good theory! I'll go through the consonants and see if it's true. If you have any ideas as to why it should be that way, please write an answer. I have no clue, other than it sounds better that way.
    – Joonas Ilmavirta
    Commented Feb 2, 2017 at 19:28

1 Answer 1


I went through all Latin consonants. All consonants seem to prefer only one of e- and ex-. I have only listed one example per consonant. There are no (or only few and rare) verbs starting with X or Z.

The prefix e-:

  • B: (e)bibere
  • D: (e)ducere
  • G1: (e)gerere
  • I2: (e)iurare, eicere < iacere
  • L: (e)loqui
  • M3: (e)mergere
  • N: (e)numerare
  • R4: (e)rumpere
  • V5: (e)vertere

The prefix ex-:

  • C: (ex)cedere
  • F: (ef)ferre
  • P: (ex)pellere
  • Q: exquirere < quaerere
  • S6: (ex)secare
  • T: (ex)tollere

1 L&S mentions exgurgitare as a synonym of egurgitare. I found no other such verbs.

2 I only included the consonantal I (or J). For vocalic I the prefix is ex-: ire > exire.

3 L&S mentions exmovere as a synonym of emovere. Otherwise e- is always used before M.

4 L&S mentions exradicare as a synonym of eradicare. There is also a rare exrogare.

5 I only included the consonantal V. For vocalic U (or V) the prefix is ex-: urere > exurere.

6 The exs- can become ex-; consider existere < sistere.

Conclusion: Voiced consonants take the prefix e-, unvoiced ones take ex-. There are very few exceptions. I have no idea why this is the way it is, other than it sounds more natural this way. See TKR's comment below for an explanation.

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    This rule is part of a larger pattern: Latin generally disallows s before a voiced consonant, and historically such an s was lost, along with any consonant that immediately preceded it, and with compensatory lengthening of the preceding vowel. For example, vēlum 'sail' < wekslom, *āla 'wing' < aksla, *trēdecim '13' < *trēsdekim. It's thought that in such cases the [s] first became [z] by voicing assimilation and later was lost.
    – TKR
    Commented Feb 3, 2017 at 0:57

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