The concept of solidarity contains an ambiguity in terms of its use in social sciences. Although it is
one of the concepts used in subjects such as the formation of the social order, determination of the conditions, providing of the social integration within the discipline of sociology, it has not been a subject for detailed analyses like the concepts of “freedom”, “justice”, or “equality”. As a matter of fact, there is not a single work regarded as a classic related to this concept. The concept of solidarity, which has not been discussed as a separate subject within sociology, has been associated with subjects intersecting by many fields. In these studies, the striking point is that researchers use the concept differently from each other and ascribe specific and superficial meanings for the most part according to the subject. Also, the concepts’ having broad meanings spreading across many fields such as sociology in particular,as well as ethics, politics and political philosophy; the concepts’ being mainly aimed at community structures, and the modern world’s externalizing the formation like community; social relations’ transforming into a vague structure by being anonymized etc. are among the factors ambiguating the meaning of the concept of “solidarity”. This uncertainty about the concept of “solidarity” will oblige us to analyze the concept and lead us to looking at the way the concept was used by experts (philosophers and sociologists). Referring to the historical background of the concept of “solidarity” in the world of the western thought, the study aims to reveal how it was discussed by the thinkers connected with modern sociology in the 20th century such as Adorno, Habermas and Rorty.