The present article is devoted to the study of “S” in modern English grammar. It examines the behavior of this operator in the English language. Thus, the study shows that this marker plays a very important role in the functioning of this English language. Its origin and status have created a lot debates around the linguistic and grammar fields. Though there have been some studies on its history, many speculations on its origin have been based on inferences from synchronic variation. In addition, focusing on its function and position towards the verb or the noun we have pointed out “S” can be used as verbal agreement marker or as noun agreement marker. In so doing, the role it plays, as a verbal marker is totally different from the one its plays as noun marker. But this current study is focused on its status as a verbal agreement marker.