In English and many other languages, many verbs may be in either an active form or a passive form. Most descriptions of the passive treat the active as a more basic form, with the passive derived from it.
The easiest way—perhaps the only way—to describe active or passive is by the relationship between them: the subject of an active verb is not present in the corresponding passive form, or is demoted in the passive to become more peripheral. In more detail:
- the subject of an active verb is either not present at all in the passive sentence or is demoted to become only a peripheral part of the passive sentence—for example, an indirect object, oblique object or prepositional object.
- in some languages, the direct object of an active verb is promoted to become the subject of the corresponding passive verb.
- some languages mark a passive verb explicitly to show that it is passive.
The rest of this post gives an example contrasting the active and passive in English, explains how English forms the passive from the active and discusses why writers and speakers use the passive. The post also mentions 2 other English constructions that resemble the passive in some respects and comments briefly on traditional terminology that refers to active and passive voices.
Example of English active and passive
Consider the following 3 sentences:
(1) She greeted them. [active]
(2) They were greeted. [passive: short version]
(3) They were greeted by her. [passive: long version]
To show clearly the grammatical cases used in the active and passive forms, I selected these 3 sentences containing pronouns, rather than nouns. In English, only pronouns have different forms for nominative case and accusative (or objective) case, as discussed at https://languagemiscellany.com/2021/12/does-english-really-have-case. The discussion below refers to noun phrases, which could include single nouns, pronouns or phrases headed by nouns. (Some theories of syntax use the label determiner phrases instead of noun phrase.)
Also, the examples I selected contain a verb denoting an action (greet). It is beyond the scope of this post to discuss which types of verb can have a passive form.
Sentence (1) is a sentence in the active. The grammatical subject (she) performs some action (greeted) on the grammatical direct object (them).
Sentences (2) and (3) are passive versions of the active sentence (1). Like some other languages, English has both short and long versions of the passive. Only the long version includes the noun phrase that is the grammatical subject of the corresponding active verb.
Forming passive from active in English
In English, the relationship between active and passive sentences is as follows:
- The subject (she) of the active verb is either not present at all in the passive (sentence (2)) or is demoted to become a prepositional object (by her, sentence (3)).
- All complete English sentences require a grammatical subject. Thus, the direct object (them) of the active verb is promoted to become the subject (they) of the corresponding passive verb.
Because this promoted noun phrase is the grammatical subject: it precedes the verb; it is marked as being in the nominative case (they instead of them); and the person and number of the verb agree with the person and number of the grammatical subject (were greeted is 3rd person plural, agreeing with they). - The form of the verb marks it as passive. The English passive contains an auxiliary (were) and a past participle (greeted). The English passive auxiliary is generally the auxiliary verb be, but sometimes the verb get can replace the auxiliary verb be. The past participle is an adjectival form of the verb.
The past participle doesn’t just appear in the passive. It is also part of the active form of the perfect tense: She has greeted them.
Why use the passive?
The passive:
- is useful when the underlying subject of the corresponding active form is either unknown or unimportant.
- states something about the underlying object of the corresponding active form, rather than about its subject. Mary greeted Brian and Sarah states something about Mary. Brian and Sarah were greeted by Mary is a statement about Brian and Sarah.
Many style guides warn against over-use of the passive. That is good advice, but sometimes goes too far, as discussed at https://languagemiscellany.com/2021/05/fear-and-loathing-of-the-passive/
Other English constructions
The passive differs from 2 other constructions in English. The first of those constructions is a purely adjectival use of the past participle, following a form of the verb be. This construction sometimes looks identical to a passive form. For example The window was broken can be either:
- a passive sentence (describing an event and corresponding to the active form someone broke the window); or
- the verb be followed by the past participle used adjectivally (describing a state, in the same way as the window was open).
A second construction is an alternation between transitive and intransitive forms of the same verb. An example is the alternation between he broke the window (transitive) and the window broke (intransitive). This intransitive form is similar to the passive because:
- the subject of the transitive version (he) is removed; and
- the object of the transitive version (the window) is promoted to become the subject.
Nevertheless, the intransitive version is not passive because the verb is still marked as active (broke), not as passive (was broken).
Terminology
Traditional descriptions refer to active verbs as being in the active voice and passive verbs as being in the passive voice. It is useful to have some term to separate the distinction between active/passive from other distinctions. Other distinctions made for verbs include tense (eg past/present), mood (eg indicative/subjunctive) and aspect (eg imperfective/perfective).
I have not used the term voice in this post. The meaning of that term is unlikely to be clear to most readers.
Summary
Converting a verb from an active form to a passive form makes the subject of the active form less prominent or deletes it entirely.
Also, in English at least, switching from active to passive changes what a sentence is commenting on. An active verb comments on that verb’s subject. A passive verb comments on its own subject—which is the same as the active verb’s object.