Pretérito de ser:

fui, fuiste, fue, fuimos, fuisteis, fueron

Pretérito de ir:

fui, fuiste, fue, fuimos, fuisteis, fueron

¿Cómo han evolucionado los verbos "ser" e "ir" para tener la misma conjugación en el pretérito (y también en el imperfecto y el futuro de subjuntivo)? ¿Y por qué las formas en el pretérito empiezan por "fu-"?


Preterite of ser:

fui, fuiste, fue, fuimos, fuisteis, fueron

Preterite of ir:

fui, fuiste, fue, fuimos, fuisteis, fueron

How did the verbs ser and ir evolve to have the same conjugation in the preterite (and also in the imperfect and future subjunctive)? And why do their preterite forms begin with fu-?

  • 1
    I'm not sure if this in an example of "suppletion" or an example of the opposite of suppletion \-: There's probably a good question for the linguistics site in it though! Commented Nov 16, 2011 at 18:07
  • 1
    I am editing this question to be entirely in English, instead of a mix of Spanish and English. If you believe an exception should be made for this question, please weigh in on the meta discussion about this (and similar posts): meta.spanish.stackexchange.com/q/86/12
    – Flimzy
    Commented Nov 26, 2011 at 17:38
  • 2
    Portuguese follows the same pattern
    – andrerpena
    Commented Feb 9, 2012 at 15:19

2 Answers 2



Lo he oído explicado así:

El pretérito de "ser" viene de la versión del latín de esse, que usa la raíz 'fui'.

La historia va de que "ir" es irregular en el sentido de que estaba compuesto de múltiples verbos, y por tanto toma su pretérito del latín "esse".

  • El presente, pretérito, subjuntivo del latín vadere.
  • El infinitivo del latín ire.
  • El condicional y el futuro vienen del infinitivo.


I've heard it explained this way:

The preterite of ser is from the latin version of esse, which uses the 'fui' root

The story goes that ir is irregular in the sense it was composed of multiple verbs, and therefore borrows its preterite form from the latin esse.

  • Present, preterite, subjunctive from Latin vadere.
  • Infinitive from Latin ire.
  • Conditional and future are from infinitive.
  • 4
    Ah yes well the composition of ir from multiple verbs is definitely a case of suppletion. The use of some forms in multiple verbs is something I'm not sure there's a term for. Commented Nov 16, 2011 at 18:11
  • 1
    I think the second link (vadere) is wrong - I get the conjugation table of the verb videre (to see).
    – kodkod
    Commented Nov 22, 2011 at 16:30
  • 2
    The preterite of ser is from the latin version of esse, which uses the 'fui' root You are just restating the presupposition from the question. Commented Feb 10, 2012 at 23:11
  • 2
    Although it is all true, it is not an answer to the original question. It is just the same said in different wording. Commented May 15, 2016 at 11:15
  • Does the preterite of ir come from Latin vadere? It reads fui instead of something similar to vasi (Latin active indicative present perfect).
    – iBug
    Commented Jan 25, 2019 at 5:42

Both ser and ir are suppletive verbs, which means that their conjugations are the result of multiple verbs merging together in the past, some conjugations taken from one root verb, and some from the other. It so happens that one of the root verbs was shared by both of these: Latin esse, some of whose conjugations began fu-. Note, esse itself was formed by suppletion of two pre-latin verbs, see the following chart:

enter image description here

Now, the question of why ir suppleted with esse ("to be") is a semantic one, and non-rigourously one can imagine how "I was [there]", "I may be [there]" etc (esse) might come to mean the same as "I went [there]", "I may go [there]" etc (ire):

for ire + esse: if you ‘are’ somewhere, it follows that you ‘went’ there. For example, you can say “I’ve never been to Barcelona” instead of “I’ve never gone to Barcelona”.

Related: https://linguistics.stackexchange.com/questions/27254/are-the-english-words-essence-and-essential-related-to-the-spanish-word-ser

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