(I am not a linguist, so I don't know proper terminology)

When studying Spanish and French, I quickly learned that many very common verbs have irregular forms; the reason given was that common usage gave way to more possibilities for the word to change.

Why then is the word "brother" (same for "father" and "mother", etc), such a stable word in Indo-European languages, given that it is clearly a very common noun?

  • 1
    It'd help to put an actual question as the title. I'm thinking something like, "Why are some common words so stable across the Indo-European languages while others have such variation?" Although I'm also not a linguist.
    – wjandrea
    Feb 5, 2023 at 21:37
  • Just a little notice about the article, barát in Hungarian means "friend", brother (or sister as there's no distinction) is "testvér" which has nothing to do with PIE as it's a compound of 2 Finno-Ugric words (meaning body and blood), not sure if that's relevant since Hungarian is not Indo-European but I'm just questioning its mention in the article
    – mi1000
    Feb 6, 2023 at 8:03

1 Answer 1


Common usage creates irregularity, but not because those words are likely to change—rather, it's because they're not likely to change! These common words are likely to stay in their current forms even as the rest of the language changes around them, leaving them as irregularities to be memorized.

The way you conjugate verbs in English looks quite different from Spanish and French, for example. But English "is", Spanish es, and French est look quite similar (and quite different from how verbs work in the rest of the language). This particular form goes back to *h₁es-ti, a perfectly normal way of conjugating the verb in Proto-Indo-European, which has stuck around in various descendants despite the whole system of verb conjugation evolving in new directions. (Similarly Russian jest', Hittite ēszi, Sanskrit asti, Persian ast…)

  • 1
    Can we work-out what the old grammar rules were based on irregular verb forms?
    – Arcanus
    Feb 5, 2023 at 18:22
  • 3
    @Arcanus Yep! Looking at fossils and irregularities in recorded languages is a good source of information about their ancestors.
    – Draconis
    Feb 5, 2023 at 18:28
  • @Arcanus a case in point is that the present tense of German "sein", Latin "sum" (apart from its 1st person singular), & Sanskrit "asti" all preserve the old ablaut pattern of athematic root verbs between 3rd person singular *h₁ésti & 3rd person plural *h₁sénti, an alternation that is lost almost everywhere
    – Tristan
    Feb 6, 2023 at 10:04
  • 1
    @Arcanus See linguistic reconstruction for more details on working things out.
    – J D
    Feb 6, 2023 at 21:22

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