The following particularities of subject-verb agreement help clarify the meanings of complicated constructions in Spanish. For example, consider that word order in English tends to follow the convention subject, verb, indirect object, and then direct object whereas in Spanish these elements are interchangeable. This capability renders the possibility to use plural or singular verbs depending on whether they appear before or after its subject. And because Spanish allows tacit subjects in all persons, unlike English, which allows tacit verbs only in the second person, agreement in person and number between subject and verb may confuse native English speakers.

The following rules, based on those set by RAE on the Diccionario Panhispánico de Dudas, must be considered to determine the number and person of the verb that must be used. If you click the EN ESPAÑOL button, open another window with the tab that includes the Spanish version of the particularities of subject-verb agreement of the English language, and place it next to this one, you can compare the particularities of both languages.

1. The subject is plural if its parts are joined by the conjunction y.

[Juan y Miguel] [estudian en la biblioteca.]

But if the parts of the subject refer to the same entity or designate an aspect of a whole, a singular verb may be used.

[El escritor y político][disfruta ir a la playa.]

[La determinación y dedicación] [soluciona el problema.]

When the parts of the subject are abstract or uncountable nouns and appear after the verb, a singular verb should be used.

[Me interesa] [la filosofía y la historia.]

Infinitives, noun clauses, and neutral pronouns joined by the conjunction y require a singular subject.

[Bailar y cantar] [es lo que le gusta.]

Yet if the neutral parts are presented as distinct, contrasted, or confronted realities, a plural verb should be used.

[Correr y nadar] [son sus dos pasiones.] ^[1]

2. The conjunction o can be used either to join parts of a subject or to exclude them, making only one of the parts the subject. When it used to join singular parts of the subject, a singular or plural verb may be used.

[La sal o el azúcar][da sabor.]

[La sal o el azúcar][dan sabor.]

But when it excludes singular parts of the subject, a singular verb should be used.

[{Si un niño o una niña} {comete la misma travesura}] [es disciplinado de manera distinta.]

But if the conjunction o expresses indifference to what subject is used, a singular or plural verb may be used.

[El teléfono celular o una computadora][puede servir para conectarse a internet.]

[El teléfono celular o una computadora][pueden servir para conectarse a internet.]

If a plural adjective follows the parts of the subject, a plural verb should be used.

[La leyenda o la ficción históricas] [no son del todo imaginarias.]

If the subject is the sum of all the parts and the conjunction o joins the last two of them, a plural verb should be used.

[El lomo saltado, la causa rellena, el ají de gallina o el tacu tacu] [son algunos platos peruanos.]

If the conjunction o refer to the same thing or person, the verb should be singular.

[El coche o automóvil deportivo] [cuesta más que las camionetas.] ^[1]

3. Because terms like junto con, además de, así como and even con work as conjunctions and prepositions, determining what verb to use may seem complicated. If a singular part is joined by any of these terms to another singular or plural part that, a singular verb is preferred but a plural verb may be used.

[La niña, junto con su perro,] [corrió por el jardín.]

[El profesor con el estudiante] [asistieron al evento.]

A plural verb gives way to the possibility of using a tacit first-person singular pronoun joined to an expressed third-person singular part that would allow the use of a plural verb. However, this construction should be avoided because it may confuse readers—they could interpret the tacit part as a third-person plural pronoun.

[(Yo) Con Juan] [fuimos a pescar.]

[(Nosotros) Con Juan] [fuimos a pescar.] ^[1]

4. If a collective noun is the subject of a sentence, the verb (and the pronouns or adjectives modifying it) should be singular.

[La familia] [viajó a Estados Unidos porque la invitaron a la ceremonia.]

But if a copulative conjunction joins two sentences, the verb in the second sentence should be plural if the tacit subject is plural.

[El equipo] [celebró la anotación], y [(ellos)] [recorrieron todo el estadio cuando acabó el encuentro.]

If the copulative verb ser is used, a singular verb should be used when the subject complement is an adjective.

[Esa gente] [es mala.]

But a plural verb should be used when the subject complement is a noun.

[Esa gente] [son campesinos.] ^[1]

5. Copulative verbs need to agree with subjects in number and person. But if the atributo, which is the subject complement, is a personal pronoun, the verb should agree in number and person with it.

[La ternura] [somos nosotras.]

And if the subject and the atributo are both nouns, the verb should agree with the plural one.

[Mi miedo] [son los terremotos.]

But if one of the nouns has a collective meaning or refers to a single idea, the verb should be singular.

[El costo total del automóvil] [es treinta mil dólares.] ^[1]

6. The constructions uno de los que, yo soy (uno) de los que, and tú eres (uno) de los que require a plural verb because the subject is the relative pronoun los que/las que (the antecedent uno has been elided in the second and third construction).

[Uno de {los que} {representaban a la universidad}] [ganó en natación.]

If one of these constructions is part of the atributo, which is the subject complement, in a sentence with a copulative verb and the subject is a pronoun in singular first or second person, the verb of the relative clause should be in third person.

[Yo] [soy (una) de {las que} {trabajan mejor por las mañanas}.]

The constructions yo soy el que (o quien), tú eres el que (o quien), él es el que (o quien) do not have an expressed antecedent. When the subject is a pronoun in first or second person, the verb in the relative clause should be third person singular.

[Tú] [eres {la que} {sospecha de mí}.]

But when the subject is a pronoun in first or second plural, the verb should agree with it.

[Nosotros] [somos {los que} {llamamos a la policía}.] ^[1]

7. In general, quantifiers followed by the preposition de and then a plural noun form plural subjects when the plural noun is determined to be the nucleus of the subject, and so need a plural verb; sometimes, however, the singular quantifier serves as the subject, and so needs a singular verb. But when they are used with copulative verbs that link to an atributo, which is the subject complement, or used in sentences with predicative verbs that have a complemento predicativo, which is an adjective or noun phrase (that needs to agree in gender and number to the subject or the direct object it modifies) used in sentences with predicate verbs, the verb should be plural:

[Una minoría de estudiantes] [son hispanos.]

[Una minoría de estudiantes] [resultaron heridos.]

When quantifiers are used without a determiner, which establishes the singularity of the quantifier, the plural subject requires a plural verb.

[Multitud de profesores] [manifestaron su desacuerdo contra la ley promulgada.] ^[1]

8. Plural subjects that include the person who speaks require plural verbs in first person and those that include the person spoken to require plural verbs in second person.

[Los escritores] [necesitamos leer mucho.]

[Los escritores] [necesitan aprender gramática.] ^[1]

9. If two or more ordinal adjectives modify a single singular subject, a plural verb should be used.

[El tercer y cuarto piso] [son los que reciben mayor luz.] ^[1]

References