What is the point of 有り難う?

WaniKani uses vocabulary words that are always or mostly written in hiragana because its goal is to teach Kanji readings. But, if the role of vocabulary is to help us learn the Kanji, why がと is not listed as a kun’yomi for 難?

Because it’s not a kun’yomi reading. It’s an exceptional reading.


難い (かたい) is the reading that this is based on, and it’s true that WK doesn’t include it… but I don’t think it’s that big of a deal.

A combination of rendaku and classical grammar are what make it into がとう in that word.

It’s the same grammar that makes the はやい part of おはよう into はよう, and the めでたい part of おめでとう into めでとう, etc.

But in any case, something doesn’t have to be listed as a reading for it to be something that helps you read the kanji. You won’t find anything related to きょう on the pages for 今 or 日, but it’s how you read that word.


It’s actually quite a strange change.
Originally adjectives in the attributive form ended in -ki. So the adjective katashi (hard, difficult) would be kataki before a noun. This has become katai in modern Japanese, so the k was lost.
The adverb form was kataku. The k was added back here in modern Japanese.

However! In some common expressions the k did not get added back in.
so the “kataku” in “arigataku” (with rendaku) became “arigatau”
In a later period “-au” was changed to “-ou”.

hayaku -> hayau -> hayou
medetaku -> medetau -> medetou


Thanks for the answers, is there an automatic way to write “solved in post x by person y” ? I’m trying to add this as an edit but can’t figure out how to establish the link to the answer.

Each post should have a square with a checkbox. Click the one in the post you consider the solution.

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