Ser

Ser is the infinitive of the verb meaning “to be” in Spanish and Portuguese. It is used to express permanent or essential characteristics, identity, origin, time and dates, and material or possession. In Spanish it contrasts with estar, which covers temporary states or locations; in Portuguese a similar distinction exists between ser for lasting attributes and estar for temporary conditions. Examples include: Yo soy profesor; Ella es mexicana; Madrid es la capital de España; Esta casa es de Juan.

Etymology and scope: Ser derives from the Latin esse, the root of existence in many Romance languages. It has cognates across the family, such as French être and Italian essere. The verb functions as a core existential and classificatory verb in both Spanish and Portuguese, underpinning statements about what something is, where it comes from, or when events occur.

Conjugation and forms: Ser is irregular in both languages, with distinct present-tense forms and other tenses. Spanish present indicative: soy, eres, es, somos, sois, son. Preterite: fui, fuiste, fue, fuimos, fuisteis, fueron. Imperfect: era, eras, era, éramos, erais, eran. Portuguese present: sou, és, é, somos, sois, são. Preterite: fui, foste, foi, fomos, fostes, foram. Imperfect: era, eras, era, éramos, éreis, eram. The verb also appears in subjunctive and conditional forms and can function as the copula in nominal predicates.

Usage notes: Beyond its grammatical role, ser is often used for defining essence, identity, origin, material, and possession, as well as for the passive voice in certain constructions. In philosophy, ser appears in phrases meaning “being” or “existence,” such as discussions of the ser humano (the human being).