Vu̍t-chṳt (物質) chhai khô-ho̍k ke thin-ngi hàn-màng khok-thin, yit-pân he chṳ́ put-pien chṳt-liong (不變質量) m̀ he 0 ke tûng-sî. Vu̍t-chṳt ya cho-tet yung-lòi thúng-chhṳ̂n só-yû voi phî ngìn khon to ke vu̍t-thí ke sṳ̀n-fun.
