The analysis so far has demonstrated that the two most important concepts of solidarity in politics in Europe exhibit both similarities and differences. Although the main tendency has been for the two concepts to become increasingly similar, they have not converged completely. The four aspects of solidarity (its basis, goal, inclusiveness and collective orientation) are configured in different ways in the two concepts. These configurations vary between different times and occasions, and this make them both flexible and applicable in party programmes and political debates. Moreover, the flexibility and ambiguity is enhanced because the two different concepts are located in two different conceptual contexts or political languages. These languages are constituted by the existence of other key concepts, many of which are as flexible and ambiguous as the concept of solidarity. As a consequence, the meaning of solidarity changes not only according to how the different aspects of solidarity are combined, but also through the different meanings of these other key concepts and how these are related to the different meanings of the concept of solidarity. Consequently, it is necessary to identify the other key concepts in the social democratic and Christian democratic language and to discuss how these are related to solidarity. This is the task in this chapter. I shall conclude with a discussion about the role and the advantages of the modern language and concept of solidarity for social democratic and Christian democratic parties.