This textbook offers students an understanding of the principles and practices of using large language corpura in explanatory learning and English languages teaching and research. It focuses on the largest and most representative corpus of spoken and written data compiled - the British National Corpus - and on the search tool SARA (SGML Aware Retrieval Application). Students are taken through a graded series of exercises, which at the same time introduce features of the software and new techniques or applications for computer-assisted language learning.