This document discusses national languages and language planning. It begins by defining a national language as the formal language of a country, using Indonesian as an example. It then discusses the functions of a national language in uniting different cultures and serving as the main tool of communication. The document next covers topics like the selection, codification, elaboration, and acceptance aspects of planning a national official language. It provides examples like Samuel Johnson's dictionary helping codify English. The document concludes by mentioning how sociolinguists can contribute to acquisition planning by increasing a language's users through education and media.