This document discusses diglossia, bilingualism, and multilingualism. It defines diglossia as a situation where a community uses two different languages or variations of the same language for different situations. An example given is Arabic-speaking communities that use formal Standard Arabic for official settings and a local dialect in daily life. Bilingualism is defined as the ability to speak two languages. Benefits include easier communication and increased knowledge. Multilingualism refers to using more than two languages, as is common in parts of the world where daily life requires knowledge of multiple languages. Research on discourse in multilingual contexts often uses the term "code-switching" to describe language use without distinguishing languages from dialects.