Ma'anar ƙamus na kalmar "shaka" shine shakar iska ko wasu abubuwa cikin huhu. Wannan shi ne tsarin shan iska ko wani abu a cikin jiki ta hanyar shaka ta hanci ko baki. Kishiyar fitar numfashi ce, wato tsarin fitar da iska ko wasu abubuwa daga huhu. Shakar shakar wani muhimmin tsari ne ga masu rai yayin da yake ba su damar samun iskar oxygen da sakin carbon dioxide, wanda ya zama dole don rayuwa.