This document is a presentation on language diversity and endangered languages. It discusses that there are over 6,000 languages in the world, though many are endangered and some have been lost. Reasons for language endangerment and loss include forced assimilation policies, loss of language domains and contexts of use, and population decline. Revitalizing endangered languages is possible, as shown through the examples of Hebrew, Maori, Hawaiian, and Wampanoag. Stages of language revitalization include increasing domains of use from the home to schools, media, and government. When fully revitalized, a language can transcend diglossia and be used in national-level domains.