Japanese verbs can take the suffix -tai, which attaches to the ren'youkei form and turns the verb into an -i adjective, expressing desire to do what the verb says. I have recently wondered where this suffix comes from. Is it known? I mean, do we know where the -tai suffix in question comes from? Someone proposed it might be from -te + ai, love, as a comparison with how "oi", to love, means also to want in Hakka. Could that be?

1 Answer 1


According to this article in Japanese WP, -たい is the descendant of Middle Japanese -たし (-tasi), which ultimately traces back to Old Japanese (or Proto-Japonic) いたし (itasi; "sore, acute").

A paper referred by that page argues that this form has changed its meaning taking the path of "painful" → "sorely felt" → "of physiological necessity" → "of emotional necessity" → "desire".

Someone proposed it might be from -te + ai, love...

It's unlikely to be true considering the oldest attested form of this word ended in -asi, not -ai. Additionally, if Japanese speakers want to incorporate Chinese words in such a way, they never use te-form but append them directly to word stem or 連用形. For instance, -そう in 「雨{あめ}が降{ふ}りそう」 is said to originate from 相{そう} ("appearance").

  • If ai is a Chinese loanword, what would the "indigenous", "original" Japanese word for love be? Perhaps koi?
    – MickG
    Apr 27, 2015 at 5:09
  • And "ame ga orisou"... "looks like it's raining / going to rain"?
    – MickG
    Apr 27, 2015 at 5:12
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    (1) Yes, the indigenous word for love should be "koi" (lit. "yearning"). "Ai" for "love" is relatively new, being an outcome of modern translation from Western languages. (2) It's "furisou"... I think I'd put furiganas on it. Your translation is correct. Apr 27, 2015 at 5:30
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    @broccolifacemask, what of 愛づ【めづ】 (modern 愛でる【めでる】) as another Old Japanese word for "to love"? Sep 22, 2021 at 21:20
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    @EiríkrÚtlendi Nice catch. I wouldn't say it exactly means "romantic love", but matches up very well with English love. Sep 22, 2021 at 22:13

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