# Bi- and di- prefixes connoting "two" **URL:** \ **Category:** Factual Questions\ **Created:** [November 10, 2007, 8:20pm UTC](https://boards.straightdope.com/t/bi-and-di-prefixes-connoting-two/425956 "2007-11-10T20:20:02Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [November 10, 2007, 8:20pm UTC](https://boards.straightdope.com/t/bi-and-di-prefixes-connoting-two/425956/1 "2007-11-10T20:20:02Z")
Where exactly do these two prefixes come from, and how did they get from there to here? -FrL- ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [November 10, 2007, 8:43pm UTC](https://boards.straightdope.com/t/bi-and-di-prefixes-connoting-two/425956/2 "2007-11-10T20:43:33Z")
Bi- is Latin and di- is Greek. Now try to figure out hemi, demi, and semi! ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [November 10, 2007, 10:09pm UTC](https://boards.straightdope.com/t/bi-and-di-prefixes-connoting-two/425956/3 "2007-11-10T22:09:10Z")
[QUOTE=friedo] Bi- is Latin and di- is Greek. Now try to figure out hemi, demi, and semi! [/QUOTE] Well, I knew that much, I guess I should have made that clear. But were they prefixes in Latin and Greek? Or are the English prefixes somehow derived from Latin and Greek words? Or what? The Latin word for two starts with d, not b, so where did the b come from? And so on. -FrL- hemisemidemiquaver! ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [November 10, 2007, 11:12pm UTC](https://boards.straightdope.com/t/bi-and-di-prefixes-connoting-two/425956/4 "2007-11-10T23:12:03Z")
According to my dictionary, both are derived from their respective words for “twice,” not the number two. There’s a good chance the Latin one is derived from the Greek one, considering everything else the Romans ripped off from them. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [November 11, 2007, 1:28am UTC](https://boards.straightdope.com/t/bi-and-di-prefixes-connoting-two/425956/5 "2007-11-11T01:28:44Z")
English “twice,” Latin “bis,” and Greek “dis” are all from the Proto-Indo-European root dwis-. The combining forms (prefixes) are twi- (Old English), bi- (Latin), and di- (Greek). PIE D regularly becomes T in English, as observed in this case. PIE D normally remains D in Greek, as observed here. I would normally expect Latin to retain the PIE D in this case too. Why it switched to B I don’t know, but my sources assure me that it’s from the same root. PIE dwis- was a form of dwo-, which gives us English two, Greek duo, and Latin duus (note retained D, as expected). This root is found in a variety of other English words as well: twin, between, twenty, twelve, etc. ---
**Author:** ![Glazer](https://avatars.discourse-cdn.com/v4/letter/g/a88e57/32.png) [@Glazer](https://boards.straightdope.com/u/Glazer)\ **Post date:** [November 11, 2007, 1:45am UTC](https://boards.straightdope.com/t/bi-and-di-prefixes-connoting-two/425956/6 "2007-11-11T01:45:27Z")
And Hemi comes from Mopar. I’m sorry, please don’t hit me. I couldn’t help myself. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [November 11, 2007, 2:15am UTC](https://boards.straightdope.com/t/bi-and-di-prefixes-connoting-two/425956/7 "2007-11-11T02:15:55Z")
In chemistry, we use bis and di alternately depending on what prefixes are already used. Example: Bis(triphenylphosphine)palladium dichloride. It’s a little more complicated than that. “Bis” is used in this case because of the “tri” rather than the “di”. Similarly: Tris(triphenylphosphine)rhodium chloride ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 11, 2007, 2:45am UTC](https://boards.straightdope.com/t/bi-and-di-prefixes-connoting-two/425956/8 "2007-11-11T02:45:25Z")
[QUOTE=friedo] According to my dictionary, both are derived from their respective words for “twice,” not the number two. There’s a good chance the Latin one is derived from the Greek one, considering everything else the Romans ripped off from them. [/QUOTE] Umm, \*dwi- is the cardinal prefix for two in [Proto-Indo-European](http://en.wikipedia.org/wiki/Proto-Indo-European_numerals). (Sort of reminds of the “What did the Romans ever do for us?” scene in MP and The Life of Brian.)