I noticed that the 2nd person of indicative present forms are a bit strange compared to Latin.

  • sum → soy
  • es → eres (French es, Italian sei, Portuguese és)
  • est → es
  • sumus → somos
  • estis → sois (French êtes, Italian siete)
  • sunt → son

The and vosotros forms don't quite match Latin. Can anyone explain how they came to be?

  • We we all want to find a logic in etymology. Unfortunately etymologic doesn't mean to be logic, and words creation and evolution is at people's whim, many times depending on confusions and lack of understanding.
    – enxaneta
    Dec 19, 2018 at 9:42

1 Answer 1


Eres most likely1 comes from the 2nd person singular future active indicative of sum, eris ("you will be").

Sois comes from the Late Latin form *sutis (formed by analogy to sumus)2:

ESTIS (re-placed by *SUTIS, analogical to SUMUS) > OSp. sodes > ModSp. sois

1. On the Origin of Spanish eres, Griffin (1994)
2. The Origin of Spanish "ser": A Phonosyntactic Analysis, Joel Rini (1997)

Note that some other tenses of ser (future indicative, present subjunctive, conditional, imperative, infinitive, past participle, gerund) aren't related to sum at all, and are inherited from the suppletion of multiple different verbs in Latin (ire, vadere, sedere).

  • 2
    Buscando en el CORDE en textos hasta el año 1300 se encuentran 685 casos de sodes por solo 63 de sois. Los registros no se igualan hasta el siglo XV (1401-1500): 691 casos de sodes por 687 de sois.
    – Charlie
    Dec 19, 2018 at 8:07

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