书信往来: keep on shuttlecocking letters; keep up regular correspondence with sb.: 常有书信往来 keep up a regular correspondence
丢失: lose 短语和例子图书馆丢失了几本书。 a few books have been lost from the library.; 丢失通知书 advice of loss; 丢失信息 dropout; 丢失质量 [物理学] missing mass; 丢失质量谱仪 missing-mass spectrometer