 So we're going to quantitatively describe a single moving point and this means we need to keep track of its location in both time and space Now as a word in English time can mean a few different things. It can mean a point in time such as what time is it? Or it can mean a duration as in how much time does it take me to swim 50 meters? In physics we write the symbol t to mean a point in time and the symbol delta t to mean a duration Now this delta t is just a single symbol. It's not two different symbols multiplying together. It's just a single thing And we calculate delta t as the end time point minus the beginning time point