When I was learning Spanish last year (I didn't feel forced), I found a peculiar irregularity: the word for I know. It was yo sé, which made no sense to me. I want to know why it is yo sé and not yo sabo. Is there a Latin root?

My comparative research suggest that there is a connection because I saw the words sé/saiz,sei,so in different languages ranging from Galician to Italian. So, the root is *s- in my mind, and based off the latin word sapio/sapere.

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    There is no particular reason I know of -- after all, nobody was keeping records at the time. But whatever the reasons, the change must have happened early if it's shared with a lot of daughter languages. One possibility is that first person verbs -- especially if they get used as qualifiers -- are used a lot more, and this tends to get their edges rubbed off. Look at ain't, which started off as a contraction for am not. Oh, and it's normal for generalizations to have exceptions; irregularity is part of the system.
    – jlawler
    Oct 28, 2019 at 2:32
  • @NumberFile I don't know the answer, but staff.ncl.ac.uk/i.e.mackenzie/hisverb.htm suggests it was created by analogy to "yo hé" in the verb haber. To me, though, that begs the question of how habeo turned into in the first place... but maybe that is better known, or it is also explained there and I missed it. Personally, anyway, I don't agree that "nobody was keeping records at the time" is reason enough to brush the question off; isn't comparative linguistics partly about figuring out things that we have scant records of?
    – LjL
    Oct 28, 2019 at 15:39

1 Answer 1


A greater range of data points might allow a better comparison of the particular way the Latin verb sapio, sapere, a regular third conjugation -iō verb, ended up irregular in the Romance languages.

Compare the third person singular forms, corresponding to Latin sapit:

Italian: sa /sa/

Romansh (Grischun): sa /sa/

French: sait /sɛ/

Occitan: sap /sap/

Catalan: sap /sap/

Spanish: sabe /ˈsa.βe/

Portuguese: sabe /ˈsa.βɨ/ (PT), /ˈsa.bi/ (BR)

Galician: sabe /ˈsa.be/

We see a clear distinction, in that Occitano-Catalan and Iberian Romance kept the labial consonant /p/ in some form, whether at the end of the syllable, as /p/ or voiced to /b/ and then lenited to /β/. French, Italian and Rhaeto-Romance have not.

Contrast that with the loss of /p/ from Latin sapiō in the first person singular across all the Romance languages.

Hence, further explanation for the first person singular form is necessary. The most commonly accepted explanation for Spanish is presented below:

La forme très réduite, , issue du Latin SAPIO, s'explique par sa position souvent proclitique dans le discours et par analogie avec la forme he de haber.

The combination of often being before an infinitive [specifically first person singular] and analogy with he from haber is cited.

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