Ukuzala yikhwalithi yokukwazi ukukhiqiza inzalo ngokuzala kabusha ngemuva kokuqala kokuvuthwa ngokocansi .Njengesilinganiso, izinga lokuzala liyinani elijwayelekile lezingane owesifazane analo empilweni yakhe futhi liyabalwa ngokwenani labantu.Ukuzala kuvame ukucatshangelwa lapho kunobunzima noma ukungakwazi ukuzala ngokwemvelo, futhi lokhu kubizwa nangokuthi ukungazali.Ukuthola inzalo akubandlululi muntu othile futhi le nto yaziwa kabanzi, ngochwepheshe bezenzalo abatholakala emhlabeni wonke ukuhlinzeka ngobuchwepheshe bokusiza omama nemibhangqwana ebhekana nobunzima bokuthola umntwana. Ukuzala kwabantu kuncike ezintweni zokudla okunempilo, indlela yokuziphatha ngokocansi, amandla okuzibandakanya, amasiko, isazela, i- endocrinology, isikhathi, ezomnotho, indlela yokuphila, nemizwa. Nenzalo sehlukile fecundity, okuyinto ichazwa lungaba ukukhiqizwa kabusha (kuthonywa gamete ukukhiqizwa, kokukhulelwa futhi bephethe ukukhulelwa eside).Lapho owesifazane noma ukungabikho kwenzalo kuyinyumba ngenkathi ukuntuleka kwenhlamba kungabizwa ngokuthi inzalo.