This book is a collection of papers using samples of real language data (corpora) to explore variation in the use of English. This collection celebrates the achievements of Toshio Saito, a pioneer in corpus linguistics within Japan and founder of the Japan Association for English Corpus Studies (JAECS). The main aims throughout the collection are to present practical solutions for methodological and interpretational problems common in such research, and to make the research methods and issues as accessible as possible, to educate and inspire future researchers. Together, the papers represent many different dimensions of variation, including: differences in (frequency of) use under different linguistic conditions; differences between styles or registers of use; change over time; differences between regional varieties; differences between social groups; and differences in use by one individual on different occasions. The papers are grouped into four sections: studies considering methodological problems in the use of real language samples; studies describing features of language usage in different linguistic environments in modern English; studies following change over time; and case studies illustrating variation in usage for different purposes, or by different groups or individuals, in society.