It seems to be generally understood that transitive/intransitive verb pairs, when they are not a 四段活用 and a 二段活用 that share the same 終止形, were created by taking a base verb, whether transitive or intransitive, and adding an Old Japanese auxiliary - す for transitivity, and る or ゆ for intransitivity - to the 未然形 to form the verb of opposite transitivity. For example, [減]{へ}る (intransitive) + す = [減]{へ}らす (transitive).

But something confuses me - since auxiliaries like す、る、ゆ、ふ、etc. only attach to the 未然形, what is the deal with 二段活用 verbs? For example, [覚]{さ}む is a 下二段活用 intransitive verb, and [覚]{さ}ます is its transitive variant.

Where does this -a stem in [覚]{さ}ます come from? The 未然形 of [覚]{さ}む is [覚]{さ}め, not [覚]{さ}ま like if it were a 四段活用. Would it not logically be [覚]{さ}めす instead? [上]{あ}ぐ becomes [上]{あ}がる, [満]{み}つ becomes [満]{み}たす - all of these are 二段活用 verbs, which do not feature an -a stem in their 未然形, yet the opposite transitivity uses an -a stem. What is the reason for this?

This also seems to appear for カ行変格活用 verbs as well, as [出]{で}[来]{き}る -> [出]{で}[来]{か}す instead of でこす.

According to the Wiktionary etymology of あぢさはふ:

The initial adi is likely from the 䳑鴨 (ajigamo, “Baikal teal”),[1] while the derivation of sapapu is unknown.

One theory states from 障ふ (sapu), basis for modern 障える (saeru, “to hinder, interrupt”, transtitive) and 障わる (sawaru, “to disturb, harm”, intransitive). This is problematic as sapu is a 下二段活用 (shimo nidan katsuyō, “lower bigrade conjugation”) verb and not a 四段活用 (yodan katsuyō, “quadrigrade conjugation”) verb required for a 未然形 (mizenkei, “irrealis form”) ending in -a.

This seems to suggest that 二段活用 verbs cannot simply swap to an -a stem when an auxiliary is added (here being ふ).

There are also some verb pairs where both the intransitive and transitive verbs have auxiliaries on a non-verbal-未然形 root, like [外]{はづ}す and [外]{はづ}る, and there are also some curiosities like [消]{け}す and [消]{き}ゆ where the roots are not the same vowel. What is the reason for this as well?

  • 1
    There was a discussion about the 消つ/消ゆ case that associates it with pre-Old contraction. japanese.stackexchange.com/questions/66436/… Commented Apr 3, 2021 at 15:09
  • @brokenlaptop thanks, also I just looked at the page and realized that [出]{で}[来]{か}す is another instance of the -a stem somehow appearing, since 未然形 of く is こ. So it's not just 二段活用, it's カ行変格活用 too... interesting. Though a later か -> こ transition could be likely since this has been seen countless times, I'm not sure and don't want to make any assumptions Commented Apr 3, 2021 at 20:34
  • I find a paper about it but I don't have time to write a summary right now. So I put the link here. If I can take some time, I'll write the summary as an answer. (or if there is someone who has read this article and write answer, it's grateful)kpu.repo.nii.ac.jp/…
    – tatmius
    Commented Jul 11, 2021 at 9:40

1 Answer 1


My major is not linguistics but I found some interesting references for you.

Aoki[1] introduces a few types of classification of transitive/intransitive verbs in Japanese.

The first classification is written by Kuginuki[2]. It says there are 3 patterns of transitive/intransitive verb pairs.

  1. Depending on the type of conjugation (第Ⅰ群形式)

    知る (四段活用 is an intransitive verb and 下二段活用 is a transitive verb)
    切る (下二段活用 is an intransitive verb and 四段活用 is a transitive verb)

  2. Depending on the termination of a word (第Ⅱ群形式)

    成る (intransitive), 成す (transitive)
    寄る (intransitive), 寄す (transitive)

  3. Depending on the additional stem and additional termination of a word (第Ⅲ群形式)

    明く (intransitive), 明かす (transitive)
    上ぐ (transitive), 上がる (intransitive)

The second classification is written by Okutsu[3].

  1. Transitivization (from intransitive to transitive)

    乾く → 乾かす
    落ちる → 落とす

  2. Intransitivization (from transitive to intransitive)

    まげる → まがる
    はさむ → はさまる

  3. Polarization (from some common element to transitive or intransitive verb)

    帰る → 帰す
    アク → アケル

Kageyama[4] follows the second classification. And in [4], transitivization is classified into two patterns:

  1. intransitive verb + -e- → transitive verb

    割る (waru) → 割れる (wareru)
    抜く (nuku) → 抜ける (nukeru)

  2. intransitive verb + -ar- → transitive verb

    植える (ueru) → 植わる (uwaru)
    集める (atsumeru) → 集まる (atsumaru)

and also intransitivization is classified into two:

  1. transitive verb + -e- → intransitive verb

    建つ (tatsu) → 建てる (tateru)
    進む (susumu) → 進める (susumeru)

  2. transitive verb + -as- or -os- → intransitive verb

    鳴る (naru) → 鳴らす (narasu)
    枯れる (kareru) → 枯らす (karasu)
    起きる (okiru) → 起こす (okosu)

Aoki[1] summarizes the above as follows:

In 第Ⅰ群形式, 下二段活用 verb is derived from 四段活用動詞. And 第Ⅲ群形式 is derived from 第Ⅱ群形式.

And Aoki also says that auxiliaries る and す are derived from these suffixes.

So I personally think the matter of transitive/intransitive verbs has some relationship with auxiliaries but it seems a bit different from the way you think.

[1] AOKI Hiroshi, "On the relationship of paired yodan-shimonidan conjugation" in 京都府立大学学術報告(人文・社会), vol.53, Dec 2001, Available:https://kpu.repo.nii.ac.jp/?action=pages_view_main&active_action=repository_view_main_item_detail&item_id=4083&item_no=1&page_id=13&block_id=17 [Accessed Jul. 13, 2021]

[2] KUGINUKI Tooru, "古代日本語の形態変化", 1996, 和泉書院, Available:https://nagoya.repo.nii.ac.jp/records/14721 [Accessed Jul. 13, 2021]

[3] OKUTSU Keiichirō, "自動化・他動化および両極化転形ー自・他動詞の対応" in 『国語学』第70集, Sep. 30, 1967, Available:https://bibdb.ninjal.ac.jp/SJL/view.php?h_id=0700460660 [Accessed Jul. 13, 2021]

[4] KAGEYAMA Tarō, "動詞意味論-言語と認知の接点―",1996, くろしお出版, No PDF (I borrowed this book from a library)

  • Sorry for the late response. So it seems like, possibly, instead of a simple auxiliary that goes onto a certain base (未然形), it's more like the ク語法 situation where the suffix [所]{あく} blended into the 連体形, causing the -a- to appear everywhere regardless of the paradigm. Just pure speculation, but the -ar- intransitivation could possibly be from 終止形 + [有]{あ}る? Though あり was a ラ変... Regardless, thanks. It seems like this matter probably needs more looking into. Speculation about /a/ ↔ /o/ alternation might apply to the -as-/-os-. Commented Aug 28, 2021 at 21:22

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