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I was wondering if there are differences between the cases of using di- and the cases of using bi-?

For example,

  • why carbon dioxide instead of carbon bioxide?
  • Why binoculars instead of dinoculars?
  • Why bisexual instead of disexual?
  • Why bilateral instead of dilateral?
Tim
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1 Answers1

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Bi- comes from Latin, Di- from Greek. Which prefix is used would usually depend on the origin of the root of the word.

yoozer8
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  • Thanks! Seems like I have to learn history of each such word! Possibly any rule saying that which is used more often in what category? For example, in chemistry, di-; in social science and physics, bi-? – Tim Feb 09 '12 at 21:18
  • Precisely. Dioxide is a Greek word, whereas binoculars and bisexual are of Latin origin. +1. – Irene Feb 09 '12 at 21:20
  • You could learn the history ... or you could just accept whatever you find in the dictionary. While it is sometimes useful to know the origins of a word, 95% of the time you can just use it without having to know that it came from Latin via French or that it was coined by Hiram Slocum in 1892 or whatever. – Jay Feb 09 '12 at 22:02
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    Plenty of Latin words have the prefix di- or dis- thought they often lose the sense of 2 by the time they arrive in English: compare bisection and dissection. – Henry Feb 09 '12 at 22:51
  • @Henry: In mathematics, is bi- more often than di-? I cannot think of some examples with di-. – Tim Feb 09 '12 at 23:11
  • @Tim: from Latin there are examples such as difference and discrete and from Greek diagonal – Henry Feb 10 '12 at 07:57
  • @Henry: Thanks! But do they all mean two things? Seems like there is no word with di- and meaning two things. – Tim Feb 10 '12 at 12:07
  • @Henry: No. The Latin words in "di-" have a meaning of "apart", or "separate" (eg "differ", "diverge"), not originally "two". "Diagonal" has yet another origin, Greek "across". – Colin Fine Feb 10 '12 at 13:37
  • @Tim: Greek roots are perhaps less common than Latin ones in many branches of mathematics, but not in Geometry, where you can find "dihedral angle" (the angle between two faces of a solid). – Colin Fine Feb 10 '12 at 13:40
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    @Colin: I suspect that all of the "apart" meanings stem from "two". Wiktionary takes di- back to a reconstructed proto-IndoEuropean dwis, and bi- back to dwóh₁, both related to the English twice and two. – Henry Feb 10 '12 at 14:48
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    @Henry. Apparently so. I'm surprised, because "bis" is the normal Latin reflex of "dwis" (cf "bellum" for "duellum"), but the OED agrees that "dis-" is from that same root. – Colin Fine Feb 12 '12 at 01:37
  • @Tim: diagonal, diagram, diophantine equation, diffeomorphism, ... – Suuuehgi Jul 18 '17 at 06:55