How do the "Godan verb with u ending (special class)" verbs differ from regular u ending verbs?

Question

I came across a new word for me, 問{と}う (to ask, to inquire). I looked it up in the dictionary and it appears to be of a special class according to jisho.org. Other verbs listed under this category are 乞う,給う and 恋う.

I guess there might be some special conjugation rules that apply to this "u special class" of verbs, in a similar fashion to the special class of suru verbs (see this related QA).

By looking at some example sentences I found out that the conjugation indeed differs from that of regular u verbs in the particular case of the past form:

彼は僕にいろいろのことを問{と}うた (〇)

彼は僕にいろいろのことを問{と}った (×)

but I couldn't find more detailed information in how to conjugate this kind of verbs.

Besides conjugations, do the so called u special class verbs differ in any other aspect from regular u ending verbs?

Answer 1

Making simple what is explained in the following link, the answer is that there are no rules but there are two groups of ワア行五段¹ verbs, the one conjugating with 促音便 and the other with ウ音便.

• 「厭うて」か「厭って」か

Normally ワア行五段 verbs conjugates with 促音便 when connecting to て/た. E.g., 買う→買って, 食う→食って.

There is the other group of verbs that conjugates with ウ音便 instead of 促音便. The verbs in question fall in this category. There are some fluctuations, as mentioned in the above

「乞う」「問う」は「乞うて」「問うて」でいいとしても、ほかは「厭うて」か「厭って」か、どちらを使うか迷うところです

To me 彼は僕にいろいろのことを問うた is somewhat odd as a standalone sentence even if it's grammatically fine. The point is that most of the verbs in question are archaic and need appropriate collocations/contexts etc.

At the same time, you can hear instances of those in modern conversation. Just two that come to my mind.

• 言うても works like that said, in spite of everything. Normally 言う conjugates with 促音便(i.e., 言って). 言うても is (perhaps a bit slangy and) equivalent to そうは言っても. E.g. 言うても1万円は高い With all the good things about the product, 10000 yen is expensive (for that).
• Kansai dialect uses 買{こ}うて instead of 買って.

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¹ ワア行五段: Godan verbs with the conjugating part being わいうえお like 問わない, 問います, 問う...