It seems that for first conjugation verbs (or -e- conjugation verbs i.e. those with endings in -ю/-у, -ешь, -ет, -ем, -ете, -ют/ут), the -y ending is always used at the first person singular after any consonant except if it is :

  • an л, such as in пошлю́ (I send);
  • a ь (soft sign), such as in убью́ (I kill).

But what is the more general phonological or orthographical reason/rule of such a behavior ? Especially, why the л, which is a consonant, does not trigger the -у ending ? And why is this so only for first conjugation verbs ?

1 Answer 1


Zaliznyak's dictionary provides a comprehensive description, but in short: the majority of first conjugation verbs have so-called "transitive softening" - a synchronic counterpart to historical jotation (those verbs had -*j- suffix in present tense, which left some effects of consonants). Some, like сосать - сосу, don't, but these are exceptional and/or belong to infrequent subclasses (there's even a minimal pair: орать - ору 'shout' vs. орать - орю '=пахать'). Transitive softening adds soft л after labials, turns velars and dental obstruents to shibilants, and softens dental sonorants. Second conjugation undergoes a similar process in 1 person singular only.

In addition, after ж/ш/ч/щ у is pure orthography (traditionally, they were always soft and thus ю was superfluous; then ж and ш hardened), and after ь and vowels ю stands for j+у, rather than softness+у, and is exceptionless.

  • But why these processes apply to first conjugation verbs in all of their forms whereas it only applies to first person singular of second conjugation verbs. What is the historical, phonological or orthographical reason for such a different treatment ?
    – Xavier
    Apr 9, 2022 at 9:56
  • Well, the short answer is: in second conjugation, the marker is -i- (люб-и-ть, люб-и-шь) which only becomes j before a vowel (*люб-и-у > люб-j-у > люб-л'-у = orth. люблю). In first conjugation, when -j- is present (this is not always true, see above!), it's marker of, well, present tense as a whole.
    – Viridianus
    Apr 10, 2022 at 15:20

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