Active voice is a grammatical voice

Voice (grammar)

In grammar, the voice of a verb describes the relationship between the action that the verb expresses and the participants identified by its arguments . When the subject is the agent or doer of the action, the verb is in the active voice...

 common in many of the world's languages. It is the unmarked

Markedness

Markedness is a specific kind of asymmetry relationship between elements of linguistic or conceptual structure. In a marked-unmarked relation, one term of an opposition is the broader, dominant one...

 voice for clauses featuring a transitive verb

Transitive verb

In syntax, a transitive verb is a verb that requires both a direct subject and one or more objects. The term is used to contrast intransitive verbs, which do not have objects.-Examples:Some examples of sentences with transitive verbs:...

 in nominative–accusative languages, including English

English language

English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...

 and most other Indo-European languages

Indo-European languages

The Indo-European languages are a family of several hundred related languages and dialects, including most major current languages of Europe, the Iranian plateau, and South Asia and also historically predominant in Anatolia...

.

Active voice is used in a clause whose subject

Subject (grammar)

The subject is one of the two main constituents of a clause, according to a tradition that can be tracked back to Aristotle and that is associated with phrase structure grammars; the other constituent is the predicate. According to another tradition, i.e...

 expresses the agent

Agent (grammar)

In linguistics, a grammatical agent is the cause or initiator of an event. Agent is the name of the thematic role...

 of the main verb. That is, the subject does the action designated by the verb. A sentence whose agent is marked as grammatical subject is called an active sentence. In contrast, a sentence in which the subject has the role of patient

Patient (grammar)

In linguistics, a grammatical patient, also called the target or undergoer, is the participant of a situation upon whom an action is carried out. A patient as differentiated from a theme must undergo a change in state. A theme is denoted by a stative verb, where a patient is denoted by a dynamic...

 or theme is called a passive sentence, and its verb is expressed in passive voice

Passive voice

Passive voice is a grammatical voice common in many of the world's languages. Passive is used in a clause whose subject expresses the theme or patient of the main verb. That is, the subject undergoes an action or has its state changed. A sentence whose theme is marked as grammatical subject is...

. Many languages have both an active and a passive voice; this allows for greater flexibility in sentence construction, as either the semantic agent or patient may take the syntactic role of subject.

Examples

In the following examples the active and passive voice are illustrated with pairs of sentences using the same transitive verb.

Language	Active voice	Passive voice
English	The hunter saw the deer.	The deer was seen by the hunter.
French	Brackett a écrit ce livre.　(Brackett wrote this book.)	Ce livre a été écrit par Brackett. (This book was written by Brackett.)
Japanese	犬がかんだ。 (A dog bit [someone].)	犬にかまれた。　(By a dog [I] was bitten.)
German	Der Hund biss den Postboten.　(The dog bit the postman.)	Der Postbote wurde vom Hund gebissen. (The postman was bitten by the dog.)