'''KetidakkekalanNonkekal''', '''ketidakkekalan''', '''fana''', '''ketidakfanaan''', '''''anicca''''' ([[Pali|Pāli]]), atau '''''anitya''''' ([[bahasa Sanskerta|Sanskerta]]) merupakan suatu ajaran penting dalam [[Buddhisme]].<ref name="DavidsStede1921p3552">{{cite book|author1=Thomas William Rhys Davids|author2=William Stede|year=1921|url=https://books.google.com/books?id=0Guw2CnxiucC|title=Pali-English Dictionary|publisher=Motilal Banarsidass|isbn=978-81-208-1144-7|pages=355, Article on '''Nicca'''}}</ref><ref name="gombrich47">{{cite book|author=Richard Gombrich|year=2006|url=https://books.google.com/books?id=jZyJAgAAQBAJ|title=Theravada Buddhism|publisher=Routledge|isbn=978-1-134-90352-8|page=47}}, '''Quote:''' "All phenomenal existence [in Buddhism] is said to have three interlocking characteristics: impermanence, suffering and lack of soul or essence."</ref><ref name="buswelllopez42">{{cite book|author1=Robert E. Buswell Jr.|author2=Donald S. Lopez Jr.|year=2013|url=https://books.google.com/books?id=DXN2AAAAQBAJ|title=The Princeton Dictionary of Buddhism|publisher=Princeton University Press|isbn=978-1-4008-4805-8|pages=42–43, 47, 581}}</ref> Ajaran ini menyatakan bahwa semua realitas yang berkondisi (''[[saṅkhāra]]''), tanpa kecuali, bersifat "sementara, cepat berlalu, tidak kekal".<ref name="DavidsStede1921p3552" />
Ketidakkekalan merupakan satu dari [[Tiga Karakteristik|''tilakkhaṇa'']] (tiga karakteristik keberadaan)—dua yang lainnya adalah ''[[dukkha]]'' (penderitaan atau ketidakpuasan) dan ''[[anatta]]'' (tanpa-Aku atau tanpa-roh).
