In
linguistics
Linguistics is the scientific study of human language. It is called a scientific study because it entails a comprehensive, systematic, objective, and precise analysis of all aspects of language, particularly its nature and structure. Ling ...
, a grammatical patient, also called the target or undergoer, is the participant of a situation upon whom an action is carried out or the
thematic relation
In certain theories of linguistics, thematic relations, also known as semantic roles, are the various roles that a noun phrase may play with respect to the action or state described by a governing verb, commonly the sentence's main verb. For ex ...
such a participant has with an action. Sometimes, "theme" and "patient" are used to mean the same thing.
When used to mean different things, "patient" describes a receiver that changes state ("I crushed the car") and "theme" describes something that does not change state ("I have the car").
[A similar distinction is made here:
]