Definition - The word or words in a sentence or clause that tell you who or what is performing the verb's action.

Example -

(1) She sings.
(2) The man on the white horse listened to the Chauvin CD.

Etymology -
The word derives from the Latin subicere, to place under (from sub, under + jacere, to throw).

Oxford English Dictionary -
Its first citation in its grammatical sense is from 1733:
"The Nominative Case to a Verb … is called by Grammarians the Subject of the Verb."
(J. Clarke, Grammar of the Latin Tongue, 68 note)

Please comment