Many English words use the prefixes uni-, bi-/di-, tri-, quad- and so on to mean one, two, three, and four. For example:
A unicycle has one wheel, a bicycle two, and a tricycle three.
I presume these prefixes are either of Greek or Latin origin, but from what little I know of these two languages, neither uses these prefixes as their numbers. That is, in Greek you wouldn't start counting by saying, Uni, di, tri, quad, ...
You are correct, they are from Latin and Greek, we have simply inherited terms from both. There is a good reference for Latin and Greek roots over at Wikipedia:
Uni meaning one:
un-, uni- one
language of origin: Latin
etymology: unus, unius
examples: unary, union
Bi/Di meaning two:
bi- two
language of origin: Latin
etymology: bis, "twice"; bini, "in twos"
examples: binoculars, bigamy, biscotti
di- two
language of origin: Greek
etymology: δι,
examples: dicot, dipole
Quadr meaning four:
quadr- four
language of origin: Latin
etymology: quattuor
examples: quadrangle, quadrillion
And so on; there are a lot of these and I'm no expert but believe that, although some of the roots from Latin and Greek essentially mean the same, there are some constraints on which ones to use in certain circumstances (see also: hypercorrection.) But don't quote me on that, though, I'll try and look a little information up.
Octoups#Terminology no longer works. Is this a reference to the following? en.wikipedia.org/wiki/Octopus#Etymology_and_pluralisation
Aug 17, 2023 at 12:00
They do come from both Latin and Greek as follows (along with the rest, up to ten):
uni comes from the Latin unus, meaning "one"
di comes from the Latin dis, meaning "twice" (originally from the Greek prefix di- meaning "two"
tri comes from the Latin tres (Greek treis), meaning three
quadra comes from the Latin quattuor, meaning "four"
quinta/penta comes from the Latin quintus, meaning "fifth" and the Greek pente, meaning "five"
hexa comes from the Greek hex, meaning "six" (Latin is sex)
septa comes from the Latin septem, meaning "seven" (Greek is hepta) m
octa/o comes from the Latin octo (Greek okto), meaning "eight"
nona comes from the Latin nonus, meaning "ninth"
deca/deci comes from the Greek deka, meaning "ten" and from the Latin decimus, meaning "tenth"
It's true that in Latin there are words like "bis" ("twice") or "bini" ("in pairs") but the actual word "bi" is probably not a Latin word. "Two" in Latin is "duo". Taken separately, "bi" doesn't mean anything in Latin and is perhaps a borrowing from the early Basque language which isn't even Indo-European. "Bi", even in modern Basque, means "two". ("one, two, three, four, five" in Basque: "bat, bi, huru, lau, bost").
As others have mentioned, the prefixes came from Latin (and Greek), and entered the widespread lexicon from the formal, scientific origins (primarily medicine and biology), where it was an established practice to use formal Latin in the naming and description of observed phenomena.
