Are there more irregular verbs like 行く?


I thought when you have a consonant-stem verb ending with _-ku_ you replace it
with _-ita_. For example _ka **ku_** ("to write") becomes _ka **ita_**.

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




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](http://en.wikipedia.org/wiki/Japanese_irregular_verbs).

