The notion of concept is often used to justify the status of terminology as an independent discipline and yet concept is not a particularly well defined notion. The works of some contemporary philosophers specializing in language enable us to gain a better insight into the part played by concepts in language and categorization. Conceptualization cannot be separated from speech activity and so concept construction can be studied as a discursive activity. Thus, terms can be described thanks to the opposition between signified and concept, an opposition which makes it possible to improve the description of polysemy.