This paper sheds light on various definitions of the term automation. On the basis of a bibliographical study it hands out a state of the art in terms of the level of automation. The aim of the said paper is to study, analyze and discuss several definitions of the LoA proposed in the literature. On the grounds of this analysis, a set of requirements that ought to be respected by an accurate indicator were given out in order to propound a new definition of the LoA aimed at application in the manufacturing domain and its interest in order to optimize workstations. At the end of this bibliographical study, a table summarizing the list of different definitions, and the requirements that each of them meet is drawn. A proposal for a new definition of LoA as a time ratio is also presented. Furthermore, the application on an academic case study on an assembly line with 13 operations helped us demonstrate its interest.