Ma'anar ƙamus na kalmar "katin kewayawa" yana nufin wani sirararen allo da aka yi da kayan rufewa, yawanci fiberglass, wanda aka haɗa kayan lantarki kamar resistors, capacitors, da haɗaɗɗiyar da'irori da haɗin kai don samar da da'ira. Ana amfani da katunan da'ira a cikin na'urorin lantarki kamar kwamfutoci, wayoyi, da sauran na'urorin dijital don samar da da'irar da ake buƙata don yin takamaiman ayyuka. Ana kuma san su da bugu da ƙari (PCBs) ko kuma a sauƙaƙe a matsayin kewaye.