[mass noun](Astronomy)regular variation in the eccentricity of the moon's orbit around the earth, caused mainly by the sun's attraction (天文)出差
語源
mid 17th cent. (in the sense 'elevation, exaltation'): from Latin evectio(n-), from evehere 'carry out or up', from e- (variant of ex-) 'out' + vehere 'carry'