The term "Subject" refers to the main focus or topic of discussion in a sentence or conversation. In grammar, it typically represents the person or thing performing the action of the verb. For example, in the sentence "The cat chased the mouse," the cat is the subject because it is doing the chasing. In a broader context, "Subject" can also refer to a field of study or area of interest, such as mathematics, history, or science. Students often choose a subject to specialize in during their education, allowing them to gain deeper knowledge and skills in that particular area.