Abstract: This chapter explains Aristotle’s definition of time. He defines time as a kind of number of change. It is argued that when he says that time is a number, he means that it is what we count when we count nows in a certain way. In defining time as a kind of number, he is saying that it is essentially a kind of order, not (as is often supposed) that it is essentially measurable. It is argued that when he says that time is a number that it is countable and not a number with which we count, he is saying that time, though a number of a sort, is not a discrete plurality (and hence, not a number that could be used to count things). If ‘number’ is understood in the way that is suggested, then the claim that time is a number is compatible with the claim that time is continuous.

Keywords: definition, number, order, measurable, continuous, discrete, plurality,