In the first episode of Words of Europe, centered on the word solidarity, Maria Antonia Panascì traces the different meanings that the term has taken on in history from its origins in Roman law to the present day. In fact, the original legal meaning has come to embrace a more extensive concept of a political nature, whereby the idea of solidarity is at the basis of modern welfare systems. Over the centuries, the public duty to redistribute resources in an efficient and ethically sustainable manner has been added to the obligations between private individuals ("in solido"). Above the nation-states, a new level was then created, that of European law; but if, on the one hand, a consensus has not yet been reached on what solidarity actually means within the European framework, on the other it has already begun to transcend the traditional national dimensions rooted into a nineteenth-century concept of citizenship.