The purpose of this paper is to survey and confirm the concept and fundamental difference of ambiguity & vagueness. Ambiguity means that an expression of a word or sentential structure has two meanings. So, ambiguity resembles a word with many meanings and a homonym. Vagueness doesn't have two meanings in an expression and it is not a clear linguistic expression in communicating each other. Because a speaker doesn't speak clearly, vagueness is appeared in a conversational situation. There are several fundamental difference between ambiguity and vagueness. Firstly, ambiguity and vagueness have influence on sentence interpretation in other ways. That is to say, ambiguity is appeared by word with many meanings, and vagueness is appeared by a homonym. Secondly, a word is able to express many different meanings with a coordinate conjunction in a sentence structure. If a sentence or word connect each other with a coordinate conjunction, it expresses vagueness. However, if a sentence or word doesn't connected each other with a coordinate conjunction, it expresses ambiguity. Thirdly, ambiguity is not able to have a crossed interpretation in a structure of anaphoric expressions like 'do, so, too'. However, vagueness is able to have a crossed interpretation in a structure of anaphoric expressions like 'do, so, too'. Ambiguity and vagueness is differ from each other, therefore we have to be careful in using them in a conversational situation.