"Diego Collado's Grammar of the Japanese Language" by Diego Collado is a scholarly publication written in the early 17th century. This work serves as a grammar guide to the Japanese language, aiming to assist missionaries and scholars in understanding and communicating in colloquial Japanese. It is positioned as an essential tool in the history of Japanese linguistics, particularly significant during the time of European missionary efforts in Japan. The opening of this grammar details its purpose: to provide a practical overview of the Japanese language tailored for those involved in missionary work. Collado references previous works on Japanese grammar by Father João Rodriguez, elaborating on how his own grammar is a simplified and more accessible restatement for students. The initial sections focus on the structure of the language, phonological considerations, and important grammatical attributes while illustrating foundational elements through examples designed to facilitate learning and application. This establishes the groundwork for understanding the intricacies of Japanese and its relevance in the context of religious discourse at the time. (This is an automatically generated summary.)