Morphosyntactic alignment

In linguistics, morphosyntactic alignment is the grammatical relationship between arguments—specifically, between the two arguments (in English, subject and object) of transitive verbs like the dog chased the cat, and the single argument of intransitive verbs like the cat ran away. English has a subject, which merges the more active argument of transitive verbs with the argument of intransitive verbs, leaving the object distinct; other languages may have different strategies, or, rarely, make no distinction at all. Distinctions may be made morphologically (through grammatical case or verbal agreement), syntactically (through word order), or both.

For example, in English, in the dog chased the cat (transitive verb, two arguments), and in the bird flew (intransitive verb, one argument), 'dog' and 'bird' are both subjects, which is shown by their appearance before the verb, while 'cat' is different, an object, coming after the verb. Not all languages treat 'dog' and 'bird' as equivalent the way English does: in some 'cat' and 'bird' will be equivalent, while 'dog' is different, and there are yet other systems.

Transitive verbs have two core arguments, labelled A (the more active or in-control) and O, which in a language like English are subject (A) and object (O). Intransitive verbs have a single core argument, labelled S, which in English (but not in all languages) is also a subject.

(The label P is sometimes used in place of O. Note that while the labels S, A, O, and P originally stood for "subject", "agent", "object", and "patient" respectively, the concepts of S, A, and O/P are distinct both from the traditional grammatical relations "subject" and "object", and from the thematic relations "agent" and "patient": an A or S need not be an agent or subject, an O need not be a patient, even in a language where they usually are.)

...
Wikipedia