A umthondo (penises ubuningi noma penes /-n i z / ) kuyinto eyinhloko isitho sobulili ukuthi owesilisa izilwane zisebenzisa ukuba omunye nabesifazane (noma hermaphrodites ) ngesikhathi copulation.Izitho ezinjalo zenzeka ezilwaneni eziningi, ezinomgogodla nezingenamgogodla, kepha abesilisa abawuthwali umthondo kuzo zonke izinhlobo zezilwane, futhi kulezo zinhlobo lapho owesilisa ethwala khona okubizwa ngokuthi yipipi, imithondo ezinhlotsheni ezahlukahlukene ngempela i- homologous . Igama elithi ipipi lisebenza ezithweni eziningi ezingenayo, kepha hhayi kubo bonke.Njengesibonelo, isitho esingena ngaphakathi se- cephalopoda esiningi yi- hectocotylus, ingalo ekhethekile, nezicabucabu zesilisa zisebenzisa izinyawo zazo.Ngisho ngaphakathi kweVertebrata kunezinhlobonhlobo ze-morphological ezinamagama athile, njenge- hemipenes . Ezinhlotsheni eziningi zezilwane lapho kukhona isitho esingahle sichazwe njengepipi, asinomsebenzi omkhulu ngaphandle kokungenelela ngaphakathi, noma okungenani sidlulisela isidoda kowesifazane, kepha ezilwaneni ezincelisayo ezingamaphosta ipipi lithwala ingxenye ekude kwe- urethra, ekhipha womchamo womabili ngesikhathi sokuchama kanye nesidoda ngesikhathi sokuhlangana.   Iningi lezinyoni zesilisa (isb., Amaqhude nama- turkeys ) zine- cloaca (nayo ikhona kowesifazane), kodwa hhayi ipipi.