"UniProtKB Keywords constitute a controlled vocabulary with a hierarchical structure. Keywords summarise the content of a UniProtKB entry and facilitate the search for proteins of interest. Keywords are classified in 10 categories: Biological process, Cellular component, Coding sequence diversity, Developmental stage, Disease, Domain, Ligand, Molecular function, Post-translational modification, Technical term. An entry often contains several keywords. Inside a category, the keywords are stored in alphabetical order. Keywords can be used to retrieve subsets of protein entries or to generate indexes of entries based on functional, structural, or other categories."