I'm learning Spanish (AP Spanish class for senior year of high school), and something that's bothered me since I started is how many -er/-ir verbs are either irregular or have a changing stem compared to -ar verbs, which only include a few stem-changing verbs and dar.

Is there a reason for this odd disparity?

  • Welcome to Spanish Language! It seems a good question, but I would like some more information. Can you show us numbers? I mean, what is the percentage of irregular verbs for each conjugation? The more effort you show in the question, the more likely to be upvoted.
    – Charlie
    Sep 25, 2017 at 6:37
  • In reality, I think, it's mostly due to the fact that some of the more irregular verbs happen to be er/ir verbs. The ir ending is the weakest, in the sense that many verbs have actually switched from ir to ar. Ar is the only ending for new words, except for when using -ecer (which will always take -zc-, but it's a single inchoative ending, so I'm not sure we should count those all separately). But I'm not entirely sure that the ar verbs inherently stem change more or less, as stem changes derive from Latin phonetics. Sep 25, 2017 at 14:02
  • To help your question about the comment of @CarlosAlejo There are 45 models of irregular verbs, and only 6 (13 % aprox.) are the -ar verbs. If you count ALL the models regular and irregular there are 61 models, and there are 19 models from -ar verbs (31 %) which looks less dispair.
    – VeAqui
    Sep 26, 2017 at 3:51

1 Answer 1


I'm drawing a lot on this summarized history of the Spanish verb.

Spanish first-conjugation verbs (-ar verbs) descend from Latin -āre. The phonetical evolution of these verbs from Latin to Romance was fairly straightforward. Most of the irregulars in this conjugation class belong to a well-known type of "regular irregulars", which alternate e with ie (like cerrar) and o with ue (like contar) following a simple rule. (This diphthongization has to do with the historical source of the vowel in Latin, and is not exclusive of the -ar class.)

Spanish second and third conjugations (-er and -ir verbs) descend from the Latin conjugations in -ĕre, -ēre, -īre. The first two were merged early in Ibero-Romance, and some verbs then shifted from -er to -ir (a few went the other way). These two conjugations share very similar inflections.

The -er/-ir verbs did not evolve phonetically as neatly as the others because in the original Latin form there was an unstressed front vowel (/e/ or /i/) between the verbal root and the ending in some forms. This vowel regularly turned into a yod or semivowel (/j/, like English y), this being part of a general tendency in Spanish to turn consecutive vowels in hiatus into diphthongs ([eo] > [jo], [ea] > [ja], etc.).

This yod had all sorts of effects on nearby sounds. In the case of the -ir verbs, if there was a tense mid vowel in the root (/e/ or /o/) the yod raised it, turning /e/ into /i/ and /o/ into /u/. In Romance linguistics this is customarily called metaphony; it's a form of anticipatory assimilation. Metaphony is common in Romance languages and elsewhere.

The yod dissapeared after this root-vowel raising. Thus we got patterns like those in medir ~ mido ~ midió.

If there was a lax mid vowel (/ɛ/ or /ɔ/, descended from Latin short vowels), the pattern described above combined with the diphthongization already mentioned, producing a three-way alternation: morir ~ muero ~ murió, sentir ~ siento ~ sintió.

Verbs where the root ended in a velar consonant (/k/ or /g/) palatalized this consonant before front vowels (/e/ or /i/), which added other irregularities. Thus for decir, the underlying stem dec- (with metaphony, dic-) gave both [diʦe] (modern dice) and [diko] (modern digo).

There's a whole other story with the verbs that insert -g- in the first person, like tener and valer, again because of the presence of a front vowel in the ending.

Add generous doses of analogy, regularizing verbs that had only a few irregular forms, or extending the irregular forms of some very common verbs to others of the same general phonetic shape.

These are some of the factors are what made the second and third conjugations so riddled with irregularities.

  • I don't understand how you're using "alternate with." Could you explain it in a different way in a comment? Sep 15, 2019 at 0:40
  • 1
    "Alternation" is a synonym for apophony. It's a change from one sound to another that usually carries grammatical information. As examples you have the changes e→ie, o→ue in Spanish and the Ablaut /u/→/i/ in English (foot→feet, goose→geese, etc.).
    – pablodf76
    Sep 15, 2019 at 1:32
  • I don't think you can expect most people to understand that meaning of alternation! I'm not sure what to propose, sorry. Am I understanding right, that that sentence sort of means "substitute ie for e and ue for o"? Sep 15, 2019 at 2:24
  • As always, please roll back any and all edits as you see fit. Sep 15, 2019 at 2:24
  • 1
    I've accepted your edits and added a few more words, hopefully clarifying the issue a bit. I'm afraid adding more would be counterproductive.
    – pablodf76
    Sep 15, 2019 at 19:52

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