subject

1. (grammar) The noun, pronoun or noun phrase about whom the statement is made. In active clauses with verbs denoting an action, the subject is the actor. In clauses in the passive voice the subject is the target of the action.Examples: "In the active sentence ‘The cat ate the mouse’, ‘the cat’ is the subject and ‘the mouse’ is the object."; "In the passive sentence ‘the mouse was eaten by the cat’, ‘the mouse’ is the subject even though it is the target (patient) of the action, and ‘the cat’ is the agent."Antonyms: object, ;, predicate

2. (music) The main theme or melody, especially in a fugue.Examples: "The earliest known form of subject is the ecclesiastical cantus firmus, or plain song."

3. (philosophy) A being that has subjective experiences, subjective consciousness, or a relationship with another entity.

4. (logic) That of which something is stated.

5. (mathematics) The variable in terms of which an expression is defined.Examples: "Making x the subject of x² − 6x + 3y = 0, we have x = 3 ± √(9 − 3y)."