相关单词近義詞 null set 零集(空集)臨近詞emptying, empty, empty theory, empty record, empty symbol, empty medium, empty glumes, empty-nest, empty action, empty weight, empty nodule, empty tunnel相似詞empty calories, empty into sth, empty nest syndrome, empty nester, empty-handed, empty-headed, EMS, EMT, 返回 empty set