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I thought when you have a consonant-stem verb ending with -ku you replace it with -ita. For example kaku ("to write") becomes kaita.

But this doesn't happen with iku, which becomes itta, so I guess that makes it irregular – are there any other such verbs?

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Has anyone ever heard the past form of ゆく used and what is it? (ゆった? ゆいた?) – Tim Nov 26 '12 at 15:04
@Tim It is ゆきし but it is not used in modern Japanese. We do not say ゆった or ゆいた. ゆった is informally used ONLY for the past form of [言]{ゆ}う. – l'électeur Oct 12 '14 at 12:45
@非回答者 Thank you for answering my question, and bringing this topic back to my attention. – Tim Oct 12 '14 at 15:51

Teachers and intermediate language learners regularly tell beginners that Japanese has only two irregular verbs (来る and する). This is not, strictly speaking, true.

Here are some others:

  • 行く has the irregular forms 行った and 行って, as you've noted.
  • ある has the negative form ない... which is quite irregular.
  • Imperatives often seem to have irregular forms, most notably くれ from くれる.
  • Honorific verbs can be considered as having their own pattern, or breaking the rules (e.g., くださる⇒ください).
  • 問う ⇒ 問うた and 請う ⇒ 請うた, as were pointed out by @snailboat.
  • There are a few historical pronunciations that sometimes complicate this as well, such as the abbreviated する in 訳す or 達す. The 〜する irregularity also extends to the 〜じる variant in verbs like 禁じる.

More can be found on the "Japanese irregular verbs" Wikipedia page.

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The す ending in terms like 訳す or 愛す is not abbreviated -- that's actually the older original form. The longer 訳する, 愛する, 決する, etc. are actually later developments. Likewise for 禁ず -- that's the original form, comprising 禁{きん} + す, with 連濁{れんだく} causing the shift from す to ず. That ず then becomes the 一段{いちだん} verb stem じる via regular historical processes. (Note that this ず is not the negative ず in words like あらず.) – Eiríkr Útlendi May 22 '14 at 23:01

Yes, 行く/iku is an exception to the rule. Specifically, its -te/-ta form is itte/itta. However, in most ways this verb is regular, so it usually does not get included in the list of exceptions, which is only two verbs long: する/suru, and 来る/kuru.

One other point of note is that 行く is sometimes pronounced "yuku," although this is slightly less common.

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Sometimes pronounced? That is just an other reading of its kanji. And still widely used in some specific cases like train direction. – oldergod Nov 26 '12 at 4:31
Fair enough, edited to change the nuance. – AHelps Nov 27 '12 at 18:43

Here is how you derive the past tense for 行く (and the te-form, equivalently):

   past tense of /iku/  
== { past tense of X = continuative form of X + /ta/ }  
   /iki/ + /ta/  
== { generating a new word requires sound-changes }  
== { /i/ and /u/ become devoiced/disappear in-between two devoiced consonants }  
== { normally, I-replacement repairs /k/+consonant; but here, gemination }  

Basically, it comes down to a devoiced vowel resulting in a consonant-consonant sequence, and that CC sequence getting repaired somehow.

For all other -ku verbs, e.g., /kaku/, we get /kakita/ => /kakta/ => /kaita/ , using I-replacement.

So the exception with /iku/ is that gemination repairs the /k/+C sequence instead of I-replacement.

That is the only exception I know which pertains to repairs, to directly answer your question (instead of the question "what words conjugate weird?").

As to why this happens with 行く, I am not sure... in 徒然草 (1330-1332),

用有りて行きたりとも、其の事 果てなば、とく歸るべし

and even much more recently, in 不如帰 (~1898)


we indeed have proof it was, at least in writing, the continuative form plus the past(/perfect) morpheme, with no repairs. At some point, this changes, see こゝろ (1914):


so this doesn't really help us figure out anything very much at all. I can't seem to track down anything useful here.

I'd classify 問う and 請う as a different "exception" from 行く, because for whatever reason, a totally different sound change happened, from -ひた- to -ふた-. We can still see the older form here,



from 左近大將朝光 in the 後拾遺和歌集 (~1086). This -うた form is still around in the Osaka dialect and is used for the past tense and te-form regularly. It's not clear to me why there was this branch in pronunciation.

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The change in こゝろ is almost certainly due to it being written in "oral" style, something which wasn't common in literature until Natsume's time. The change was already over though I can't find any reference which pinpoints when exactly that was(And that should be hard given that oral style was discouraged for centuries). You can compare works from the same author: "少女との交漸く繁くなりもて行きて"(Maihime - 1890) "女中はまめまめしく出て行った"(Sanshou Dayuu - 1915). – jbcreix Apr 14 '13 at 7:37
what is the name for this kind of scheme? past tense of /iku/ == { past tense of X = continuative form of X + /ta/ } /iki/ + /ta/ == { generating a new word requires sound-changes } repair(devoicing(/ikita/)) == { /i/ and /u/ become devoiced/disappear in-between two devoiced consonants } repair(/ikta/) == { normally, I-replacement repairs /k/+consonant; but here, gemination } /itta/ – meireikei Dec 29 '14 at 23:22
@meireikei I'm not aware of anyone else using it in linguistics. The format is occasionally used for computer science proofs, invented/championed by Dijkstra: cs.utexas.edu/users/EWD/transcriptions/EWD13xx/EWD1300.html – Darius Jahandarie Dec 29 '14 at 23:26

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