Definition: A sentence in which the subject of the main verb is also acted on by the verb is in the passive voice. We can also say that the verb is in the passive voice. A common use of the passive voice is to indicate what happened to the subject of the sentence without saying who or what carried out the action (although the actor can be indicated in a prepositional phrase).
How it is used: The passive voice is much more common in English than in Spanish, which often uses reflexive verbs where English uses the passive voice. Writing experts usually advise against using the passive voice unnecessarily, because the active voice comes across as more lively and does a better job of conveying action.
In English, the passive voice is formed by using a form of the verb "to be" followed by the past participle. It is the same in Spanish, where a form of ser is followed by the past participle. The past participle in such cases is modified if necessary to agree in number and gender with the subject of the sentence.
Term in Spanish: La voz pasiva.
Examples in Spanish: 1. Las computadoras fueron vendidas. Note that the subject of the sentence (computadoras) is also the object acted on. Note also that the usual way of stating this would be using a reflexive construction, se vendieron las computadoras, literally, "the computers sold themselves." 2. El coche será manejado por mi padre. Note that the person performing the action isn't the subject of the sentence, but is the object of a prepositional phrase. This sentence is less likely to be said in Spanish than its equivalent in English would be. More common in Spanish would be the active voice: Mi padre manejará el coche.
Corresponding examples in English: 1. "The computers were sold." Note that in neither language does the sentence indicate who sold the computers. 2. "The car will be driven by my father." Note that "the car" is the subject of the sentence; the sentence would be complete without the prepositional phrase, "by my father," which indicates who is performing the action of the verb.