The third volume in the collected works of Professor M.A.K. Halliday, On Language and Linguistics, includes eighteen papers exploring different aspects of language from a systemic functional perspective. The papers are organized into three sections: the place of linguistics as a discipline; linguistics and language; and language as social semiotic. In addition, there is a new work from Professor Halliday, entitled The architecture of language, in which he focuses on the assumptions or working hypotheses that enabled him to explore important questions about this massive semiotic power called 'language'.