(about a document, an agreement, a right to buy or sell shares, etc.) to be no longer valid because the period of time for which it could be used has ended （文件、协议、股票买卖权等）失效，到期，终止◆Our lease on the property expires next month. 我们租用的这份房地产下个月到期。◆The offer to buy the company expired without a deal being finalized. 购买公司的出价未达成交易会自动失效。◆The August crude oil contract expires today (= today is the last day you can buy or sell contracts to have oil delivered in August). 八月份原油合约今天到期（今天是你买卖八月份交货的原油合约的最後一天）。SYNrun out
(about a period of time, especially one during which sb holds a position of authority) to end （尤指任期）届满◆The chairman's three-year term is due to expire in March. 主席的三年任期将於三月届满。