1 N-COUNT 光年（指光在1年中所经过的距离） A light year is the distance that light travels in a year. 光年（指光在1年中所经过的距离）
2 N-COUNT [usually plural] 极大的差距；极远的距离；极长的时期 You can say that two things are light years apart to emphasize a very great difference or a very long distance or period of time between them. 极大的差距；极远的距离；极长的时期 [informal, emphasis]
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She says the French education system is light years ahead of the English one.
她说法国的教育体制遥遥领先于英国。
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I had not eaten anything hot since my last dinner with Sean. It seemed light-years away.
上次和肖恩吃过饭后我就一直没吃过热菜热饭。好像已经过了很久很久似的。