Being is the first basis of recognition and the first issue for the metaphysics. Aristotle has said in different pages of the metaphysics on "being qua being" means “ to on” and emphasized, " Being has various meanings. " He, rather than 'Being', has used "being" or existent. He, in the seventh book, has said: What has long been a source of confusion is that “ what is being? ” What does “ being” mean? These meanings of existence, what effect does have on Aristotle's metaphysical system? Whether these meanings can be delivered to each or not? The meanings of "being” in Aristotle’ s thought are controversial issue among scholars. Someone like Thomas Aquinas takes five senses and Farabi three senses and Avicenna five meanings for the existent. In this paper, while analyzing Aristotle's view based on metaphysics and looking at Thomas Aquino's perspective, we have delivered four meanings for "being" in Aristotelians. (Being of per accident, being of per true, being of potentiality and actuality, being of categories) And in fallowing, for the adventure of the meaning of "being", we will pay attention to the peripatetic philosophers, especially Farabi and Avicenna, according to their philosophical principles who have considered various meanings for the existent which are very different with Aristotle's meanings.