This is the revised, updated and enlarged second edition of the first detailed descriptive grammar in English (indeed, in any language other than Japanese and more complete than even any grammar in Japanese) dedicated to the Western Old Japanese, which was spoken in the Kansai region of Japan during the seventh and eighth centuries. The grammar is divided into two volumes, with the first volume dealing with sources, script, phonology, lexicon, nominals and adjectives. The second volume focuses on verbs, adverbs, particles, conjunctions and interjections. In addition to descriptive data, the grammar also includes comparisons between Western Old Japanese and Eastern Old Japanese and Ryukyuan, occasionally with a critical analysis of various external parallels.