What 'Is' Is is a phrase used to describe the concept of being. It is a philosophical term that has been used by many thinkers throughout history, including Plato and Aristotle. The verb associated with this phrase is 'is, ' which is a four-letter word. This verb is used to express existence or identity, and is often used in the present tense. It is also used to indicate a state of being, such as when someone says 'I am happy.'