Publisher Summary This chapter focuses on languages and partitions. The notion of a language over the vocabulary includes both natural languages and the artificial languages of logic and of computer-programming theory. The notion of a natural language is much more complicated, because its structure is very rich. In a language with paradigmatic structure, there are three species of properties: (1) properties of a purely distributional (syntagmatic) character, (2) properties of a purely paradigmatic character, and (3) properties of a mixed character. The chapter also discusses several fundamental facts concerning the derived partitions. The most important partition that arises in linguistics is the partition in distributional classes. The notion of distributional class becomes more intuitive if the notion of context is introduced in it. The most frequent type of distribution in a natural language is that of equipollent distribution.