verb · to fall into enemy hands or be occupied by an invading force during a war

这座城市在战争爆发一个月后沦陷了。

verb · to sink into a low, depraved, or corrupt state of being

他逐渐在金钱的诱惑中沦陷。

verb · to sink below water or be submerged

由于气候变暖，低洼的岛屿正面临沦陷的风险。