Note: Go to the last slide for a video of the same talk at Write the Docs Europe 2015 (https://www.youtube.com/watch?v=0kg-6YCDg64). An everyday dilemma in technical communication: What do you call that “thing”? Whether you ask developers, marketing folks or users, you often get very different views. Along with user interfaces, documentation helps all stakeholders align their mental model of a product. Terminology plays a key role, and a controlled vocabulary is an ace up the technical writer’s sleeve. Controlled vocabularies are basically lists of concepts and the relationships between them. Beyond consistent naming, they are about structuring, categorizing and retrieving content. For example, you can use a vocabulary as a basis for documentation plans, tables of content, a help site’s navigation, search filters, or even to organize test cases. In this talk, I will share ways to create and maintain various types of vocabularies, and explain what each type is useful for. You can start with a flat list of terms and expand it into a glossary, a thesaurus, a taxonomy, or even a full-fledged ontology.