Ciwon daji rukuni ne na cututtuka da ke tattare da haɓakar ƙwayoyin sel mara kyau, tare da yuwuwar mamayewa ko yaduwa zuwa wasu sassan jiki Wadannan sun bambanta da ciwace-ciwacen daji, wanda ba ya yaduwa. Alamun cutar ya haɗa da dunƙulewa, zub da jini mara kyau, tari mai tsawo, asarar nauyi da ba a bayyana ba, da canji a cikin motsin hanji Duk da yake waɗannan alamun suna iya nuna ciwon daji, suna iya samun wasu dalilai. Sama da nau'ikan ciwon daji 100 suna shafar mutane. Amfani da taba shine sanadin kusan kashi 22% na mace-macen daji. Wani 10% kuma yana faruwa ne saboda kiba, rashin cin abinci mai kyau, rashin motsa jiki ko yawan shan barasa. Sauran abubuwan sun haɗa da wasu cututtuka, da fallasa hasken ionizing, da gurɓataccen muhalli. A cikin kasashe masu tasowa, kashi 15 cikin 100 na cututtukan daji na faruwa ne saboda cututtuka irin su Helicobacter pylori, Hepatitis B, Hepatitis C, Human papillomavirus infection, Epstein-Barr virus da Human immunodeficiency virus (HIV). Wadannan abubuwan suna aiki, aƙalla, ta hanyar canza kwayoyin halittar tantanin halitta.