The verb εστί in Aristotle’s de interpretatione

In this article I discuss Aristotle’s view on εστί (“is”) being a verb in de interpretaine and the significations which he explicitly attributes to “is”, and in several points the views of some of Aristotle’s commentators, including Ammonius, Boethius, al-Farabi, and Aquinas, are reported and criticized. Therefore, first Aristotle's definition of verb is examined, including its most important feature, “additionally signifying time”. In fact, "is" is due to having this feature is a verb, and thus the first signification of "is" becomes clear. After that, I discuss other two significations of "is", namely “additionally signifying combination” and "determination of truth", and the relation of these three significations to each other. Finally, it is concluded that according to Aristotle, "is" (with two objects) does not signify a categorical thing, but only additionally signifies combination. And since "is" is additionally signifying time, it can be said that for Aristotle in de interpretaione "is" is additionally signifying temporal combination.