This paper discusses the different meanings of formality and "informality," as well as the notions of legitimate work contracts. It aims at redefining the concept of "informality" based on the different principles that conduct the interpretations of economists, jurists, and the public opinion. Firstly, it presents a brief summary on the appearance of the "informality" as social problem; then, it criticizes the use of such concept, given the diversity of contractual situations included in it. It also points out the necessity of analyzing the popular notions of a "fair" work contract because the interpretations are related to economical and juridical notions of legitimate contracts. It finally examines the analytical difficulties on the theme due to the diversity of processes that generates relationships of "informality" in Brazil. It points out, then, the necessity of intensifying the academic dialog among economists, jurists, and social scientists, in order to better understand those atypical contracts.