Controlled vocabulary
From The Glossary of Digital Photography
An organized way to assign keywords to images such that the same words are used. Setting up lists of words or using specialized software are the easiest ways to do this efficiently. Call something a car one time, an auto the next time, and an automobile the third time would make finding similar images difficult. Ideally, images would have all three words as keywords, making it easy and fast to locate the images. In a controlled vocabulary, one word, automobile in this case, would be the main word to be used, and the others, auto and car, would be synonyms.
