The Polish linguist Jan Baudouin de Courtenay (1845-1929) was the first to use the term morpheme (1881, Kazan). Since then, the term has been redefined over and over again. Nowadays, the morpheme is the smallest meaningful or formal unit in a language, in a word, or in a grammar, or the smallest linguistic sign. The author of this paper gives a new redefinition of morpheme as follows: The morpheme is the smallest asymmetrical formal unit with any kind of meaning or function in word structures. The realisation of morphemes exhibits epidigmatic, syntagmatic and paradigmatic relationships or dimensions.