Un-apter is a word that means unsuitable or not fitting. There are a variety of synonyms that can be used interchangeably with un-apter, including inappropriate, incompatible, incongruous, unfitting, and unseemly. These synonyms may describe clothing that does not match, behavior that is inappropriate for the situation, or ideas that do not align with the problem at hand. Un-apter is an especially useful word because it can be modified with prefixes like dis- or un- to create new words: unadaptive for example. No matter which synonym is used, the meaning remains the same: something is not quite right, and it needs to be changed or adjusted to better fit the situation.