Ma'anar ƙamus na "ruwan ciki" yana nufin ruwan narkewar da ake samu a ciki. Yana da bayyananne, sigar acidic da aka samar da glandan ciki da ke rufe bangon ciki. Ruwan 'ya'yan itace na ciki yana taka muhimmiyar rawa a cikin tsarin narkewa ta hanyar rushe abinci da kuma taimakawa wajen sha na gina jiki. Ya ƙunshi sassa daban-daban, ciki har da hydrochloric acid, enzymes (irin su pepsin), ƙusa, da kuma intrinsic factor, wanda ke taimakawa wajen sha bitamin B12.