/-s/ will be inserted whenever its full featural specification is met. In all other cases in the present tense however, such as present or present, /Ø/ will be inserted. This is a use of underspecification, the idea that there is a ‘default’ morpheme that is inserted in the general case, and more specific morphemes that are inserted in more specific cases, when their featural specifications are met. In the above example, /Ø/ is underspecified in the sense that it is not specified for person. Underspecification relies on the ‘Maximal Subset Condition.’