Subject: The part which names the person or things we are speaking about is called the subject of the sentence. (যে ব্যক্তি বা বস্তু সম্পর্কে আমরা বলি তাকে subject বলে) - Wren & Martin
The subject is a word or a group of words that denotes the person or thing about whom or which something is said. - P.K.De. Sarkar
The subject is the agent of a sentence in the active voice- [Cliffs-TOEFL Page 40 Subject]