This book is intended to serve as a guide and foundation for the study of language endangerment and documentation. It covers briefly a broad selection of topics central to language endangerment, language vitality, language families in Nigeria, language decline and death, status and classifications of Nigerian languages and language maintenance, preservation and revitalization that could potentially prove to be of considerable interest to students, linguists and those interested in language endangerment and documentation. The speedy endangerment and death of most of our indigenous languages of Nigeria is an issue of widespread concern most especially to researchers, education planners and those interested with the question of socio-cultural identity. ethnicity and national development.