 Many languages have grammatical means to indicate the time when an action or event occurs, or when a state or process holds. This phenomenon is called tense. In English, for example, adding the morpheme -ed to the verb walk, to form walked, indicates that the event denoted by the verb occurred before the present time. What is called aspect, on the other hand, deals with the internal constituency of actions, events, states, processes or situations. For instance, it may indicate that an action is completed or still ongoing. English typically uses the -ing form of verbs to indicate ongoing processes, as in He is building a house. 