Universal accessibility is a major concern in developed countries, especially in cities. There is, however, considerable confusion about the meaning of this concept, whose definition varies from one author to another, none of which cover all the dimensions identified in all of the texts. There are also many proposals, more or less articulated, for different types of design for its achievement. The Montreal Committee for the Study of Universal Accessibility, which includes researchers and representatives from community organizations as well as a representative from the Directorate of the social diversity of the City of Montreal, undertook the job of clarifying concepts at the basis of this synthesis. This paper proposes a formal definition of universal accessibility based on a selection method and content analysis of the most relevant references. This analysis sought to better identify the nature of the concept, its purpose and context for application, its social purpose, the target population and specific group, the terms of use and the general evaluation criteria. The same procedure was carried out to define the types of design contributing to the universal accessibility and to propose classification in an evolutionary process. These clarifications are proposed as the basis for the development of an interdisciplinary, multisectoral and multidimensional approach of universal accessibility. Finally, problems related to evaluation are underlined.