🌐EnglishEnglishSvenskaРусский한국어中文日本語EntityQ5900509· pop 5· linked from 19 articlesHopf invariantHomotopy invariant of maps between spheresAvailable in 5 languages中文РусскийSvenska한국어via Wikidata sitelinks · CC0ConnectionshomotopyEntitymathematicsEntityCategoriesHomotopy theory