From Latin quattuor ("four"), originally from Proto-Indo-European

As at July 2 2021, the Etymology at the same link for quartus Wiktionary has changed.

From Proto-Indo-European *kʷeturtos ~ *kʷetwr̥tos (whence Ancient Greek τέταρτος (tétartos) and Proto-Germanic *fedurþô), from *kʷetwóres (“four”). Cognate to quadrus (“square”), from sense “four-sided”.


From Proto-Indo-European *kʷetwóres.

Cognates include Sanskrit चतुर् (catur), Old Armenian չորք (čʿork'), Ancient Greek τέσσαρες (tessares), and Old English fēower (English four).

Maybe the L. "quatt-" changed to L. "quart-", but I don't know how does this happen, and want to find one more example like this.

  • i think this word originated from quuatr but i am not sure
    – user1847
    Mar 10, 2013 at 20:03
  • 4
    I think the comment "From Latin quattuor" is misleading: it is related to quattuor, certainly, but was almost certainly generated before Latin.
    – Colin Fine
    Mar 10, 2013 at 22:09
  • @ColinFine's got it. No doubt the shift happened centuries before either quattuor or quartus were established, not in Latin but in proto-Italic or even earlier. That kind of metathesis was very common in IE languages, especially if it involved /r/ or /l/.
    – jlawler
    Jul 1, 2021 at 23:40
  • Just wondering, is the addition of an 'n' before the second 'q' from Latin 'quique' (five) to 'quinquaginta' (fifty) related or is it something completely different? Jul 2, 2021 at 7:59
  • 1
    @QuintusCaesius-RM: There is no "addition of an 'n'". Latin quinque (not "quique") inherits its 'n' from IE *penkwe.
    – Colin Fine
    Jul 2, 2021 at 12:29

2 Answers 2


The phenomenon you describe may be (adjacent) metathesis, which is not infrequent in phonology. Metathesis means "swapping". In linguistics, adjacent or local metathesis refers to the swapping of two adjacent sounds at some point in phonological developments. As to why it happens, I know of no formal explanation.

Apparently, there is something in our brains or speech apparatus that makes certain sounds less "easy" or pleasant to pronounce in combination with other forms as part of a phonological system (a language), or less easy to remember subconsciously. We are then inclined to various degrees to change pronunciation in a way that renders it closer to our common speech patterns.

A sound can simply be changed, as in the change from older English -th to modern -s in makes; alternatively, adjacent sounds can be swapped, as in iron, which apparently evolved from /(a)irən/ into /aɪə(r)n/ in modern pronunciation: the r and the schwa were swapped.

It can be seen that this is in certain circumstances a natural inclination in us humans by the frequency with which (non-Italian) children pronounce spaghetti as pasghetti; the cause is that sp- is natively infrequent in many languages, such as English and Dutch. Languages tend to sometimes transform borrowed foreign words to conform to native phonology (sound patterns).

In the case of quartus, -t- is an adjectival suffix. It is possible that at some point a form *kwat(w)rtos existed in Proto-Latin. If so, dissimilation may have been the main cause of the metathesis: a t sound twice, especially combined with a w sound twice, tends to disappear or transform in Latin, as in many other languages.

Alternatively, it may just be that the consonant cluster *-t(w)rt- was too "difficult" to pronounce, i.e. not conforming to Latin phonology, and hence transformed/simplified into -rt-. But I do not know the intermediate stages.

  • 5
    From the Lateinische Grammatik, Lateinische Laut- und Formenlehre (Leumann, Hoffmann and Szantyr, 1977: 492) *quatwortos => *quavortos => *quaortos => quartus (tw=>v, vo/uo=>o).
    – Alex B.
    Feb 17, 2013 at 17:38
  • 1
    @AlexB.: I was going to consult Ernoud-Meillet and Walde-Hoffmann...so it is simply a regular phonological transformation of tw=>v in a certain phase of Proto-Latin, I see.
    – Cerberus
    Feb 17, 2013 at 18:47
  • 1
    not exactly so. I've seen several hypotheses. de Vaan 2008 mentions Schrijver 1991's proposal that involves voicing of t and then loss of d in *du=>*u, like in suavis. I've been unable to find the explanation of what might have happened to the first *t in Ernout and Meillet 2001 and in Baldi 2002 (*kwotr-to). Leumann, Hoffmann and Szantyr 1977 say "durch dissimil. Schwund des ersten t".
    – Alex B.
    Feb 17, 2013 at 20:43
  • 1
    @AlexB.: Okay, I didn't mean to say there weren't any intermediate steps, but you seem to suggest there is no real metathesis, right? Any other kinds or sequences of changes is what I meant by "simply".
    – Cerberus
    Feb 18, 2013 at 0:30
  • 1
    Another reference. Meiser 1998: 127 also argues that there is distant (non-adjacent) regressive dissimilation in quartus, cf. "Schwund durch regressive Ferndissimilation begegnet weiter in taberna [...], sowie in quartus (§ 117,4)."
    – Alex B.
    Feb 21, 2013 at 17:27

Swapping, as @Cerberos calls it, is not a lgnuitsic process, at least not a "simply" one. Metathesis involves many steps, as does reconstruction, incidently, that shouldn't be brushed under the rug and will be explained elsewhere.

Since square and quarry are suppised to be derived from the same paradigm, it should be prudent to point out that *kʷer- is reconstructed Proto-Indo-European–implying that the questionable change had already happened and is not exclusively Latin. Germanic "four" stands to reason. There is however no strong reason to associate *kʷer- "to make, do" with quadro other than a square slab from the quarry being a piece of work.

German Würfel "die" also stands to reason. Though derived from werfen, its etymology is toobweak and too close to werben "seek employment, offer services", and by extension Arbeit (a < o regularly, oo < uo as in Norse, cp. Ođin, Wodan).

In Sanskrit is usually assumed to be the base of the word for "smith". Not only has PIE no unique word for smith, there is also no unique word for "one", or "I". Anatolian, Tocharian and Celtic disagree on those. Anatolian also has no *kʷetwóres, at least no proof of it because IIII is almost never spelled out, but there is evidence of a different word quite similar May. However, there is a chance that *kʷetu had already existed, on account of octo.

All this is to imply that "4" was an innovation.

Ergo, the metathesis explanation is an appeal to ignorance. It could be that -trt- was simplified but the more usual result would be a syllabified sonorant, similar to *(d)Kmt- "centum".

Of course, as long as I have no better explanation I can only disagree and call it uncertain. Phonotactic barriers explain at best why analogy didn't work out.

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