M.A.K. Halliday & Jonathan J. Webster 
On Language and Linguistics [PDF ebook] 
Volume 3

The third volume in the collected works of Professor M.A.K. Halliday,
On Language and Linguistics, includes eighteen chapters exploring different aspects of language from a systemic functional perspective. These 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“.