(1) Is there anything close to scientifically-meaningful to say about whether the prefix "di-" is more Latin than the prefix "bi-", when indicating two-ness?

(2) Are there published scholarly references on precisely this question, comparing the two prefixes?

(3) Are there notable Latin words which simultaneously contain "bi" and "di"?


  • In a vague sense that I have no time or experience enough to substantiate, this seems to be the case, "di-" seeming significantly more Latin-ish than "bi-" which seems more Greek-ish.

EDIT: like kindly pointed out by the responders, here this attribution of bi to Greek and di to Latin was an accidental mix-up. It is the other way round: bi is Latin, di is Greek.

  • Of course, the difference is not clear-cut, there is organic growth and randomness involved, and e.g. in Greek both "bi-" and "di-" appear in composites.

  • Both "bi-" and "di-" appear in countless scientific terms.

2 Answers 2


di- is Greek and bi- is Latin

The Proto-Indo-European root for "two" is reconstructed as *dw-. The remnants of this w can be seen in English "two", Russian dva, Ancient Greek δύο, and many other languages, as well as Latin duo, "two".

Old Latin had many words starting with dv- (where v was pronounced as English "w"). But at some point before Classical times, dv- changed into b- at the beginning of words. Hence dvellum (whence English "duel") became bellum "war", and dvonos became bonus "good".

The word duo "two" itself had a vowel u rather than a consonant v, so it avoided the change. But the prefix dvi- was affected by the change, and became bi-. A similar thing happened in Ancient Greek, which lost the w sound entirely, giving δι-.

So strictly speaking, di- should be used only on Greek roots, and bi- on Latin. But in practice Greek and Latin are mixed together all over the place and the prefix is generally chosen based on what sounds better.

(Compare also the prefixes semi- from Latin and hemi- from Greek, which are sometimes even combined, as in the musical term "hemidemisemiquaver". They're also cognates; s- before vowels at the beginning of words changed into h- in Greek.)

(ETA: Joonas suggested an even clearer pair of cognates, Latin super- and Greek hyper-. Many thanks.)

  • 3
    Perhaps a better known pair of Latin and Greek prefixes is super- and hyper-. Combining the two is a form of exaggeration.
    – Joonas Ilmavirta
    Jul 27, 2017 at 20:46
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    The reason u was kept in duo isn't frequency, but that this u was a vowel [u] rather than the consonant [w] as in duellum. Similarly for Greek δύο vs. δι-.
    – TKR
    Jul 28, 2017 at 3:58
  • 1
    It's such a shame that the modern greek word for biscuit/cookie is "μπισκότο" (biscotto), not διμαγειρεμένος or something. Jul 28, 2017 at 9:07
  • 1
    duo is from the bisyllabic *duwo-. bis is from the monosyllabic *dwi-. These two forms both go back to proto-Indo-European. It is not about the relative frequency of the two words in Latin.
    – fdb
    Jul 28, 2017 at 10:57
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    It's hemidemisemiquaver, not hemisemidemiquaver.
    – OrangeDog
    Jul 28, 2017 at 14:01

Your are confused; bi- is Latin and di- is Greek. There is no real difference in meaning between them, but in usage bi- is used with Latin constructions like bisexual and di- with Greek constructions like diglossia. bi- is not a Greek prefix.

(As an aside, I should mention that both Latin bi- and Greek δι‐ have a common origin in a reconstructed ancestor *dwi- .)

  • 8
    To add to this, Old Latin du- regularly changes to Classical Latin b-; e.g. duellum -> bellum 'war'. This is why we have both duo 'two' (disyllabic) and bis 'twice', the latter from duis (monosyllabic).
    – Anonym
    Jul 27, 2017 at 17:23
  • 3
    @Anonym. To be more precise: IE *dw becomes Latin b in initial position only. IE *du remains du in Latin in all positions.
    – fdb
    Jul 28, 2017 at 10:59

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