Does the letter "т" in Russian tend to be "ч" in its Ukrainian parallel?

Question

I noticed that "хотя бы" in Russian becomes "хоча б"`. Is it true that in the Ukrainian language letter "ч" sometimes corresponds to the Russian "т" when the words have the same proto-slavic root?" Is this a phenomenon that can be found in other parallel words in Russian and Ukrainian or it is just an exception?

I'm asking it because I learnt a little bit Russian and I study Ukrainian too, and I can find a such rule helping me to identify words more quickly.

Answer 1

First off, a small correction: it has nothing to do with the orthography (I have retagged the question); the sounds alternate, and the written letters only follow the pronunciation.

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The Consonant Alternation is a common phenomenon in Slavonic languages.

Particularly, Ukrainian has numerous cases of Alternation.

Namely, /t/ ←→ /t͡ʃ/ alternation has been caused by Iotation in Proto-Slavonic language and occurs in verbs having -ті-, -ти- at the end of the stem (hence the iotation ti → tji).

• to want — хотіти — хочу (1SG), хоче (3SG), хочуть (3PL);
• to fly — летіти — лечу (1SG), however летить (3SG), летять (3PL);
• to pay — платити — плачу́ (1SG);
• to dam up — гатити — гачу́ (1SG);
• to spin — крутити, вертіти — кручу, верчу (1SG);

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However, the case of "хоча" is even more interesting. According to Vasmer's dictionary, хоча is a remnant of Optative¹ mood of the verb хотіти, and the Optative has been usually expressed with the suffixes iê, iiê in Proto-Indo-European (PIE) and Proto-Slavonic (PSl) — mind the iotation again.

So, in Ukrainian the form -tiê has evolved into -t͡ʃa, while in russian it reduced to -tja.

Note that the russian retains -ч- in this very verb when used in 1st person singular:

• to want — хотеть — хочу (1SG).

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find a such rule helping me to identify words more quickly.

This must be the most difficult part. The phonology of Slavonic languages have a lot of sound elisions, alternations, reductions, and epenthesis. There are some formal rules that go as deep as to PIE, and many of them have exceptions, too. The /t/ ←→ /t͡ʃ/ alternation is just one of them.

This may sound unscientific, :-) but if I were you, I would not depend on deeply-buried formal rules here. Just like an English learner might be marveled with the vowel in "women"; Maybe there's a historical reason and a formal rule governing why this word is pronounced this way, but it would be easier to simply remember the word and focus on usage instead.

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⁽¹⁾ Optative is a grammatical mood that indicates a speaker's wish or hope. Speaking about its modality, it stands between the Imperative (a very strong wish) and the Subjunctive (a soft desire or hope).