延长 lengthen; extend; prolong; prolongate; elongation; extension; dwell; prolongation 延长有效期 prolong the period of validity; 条约延长十年。 the treaty has been prolonged for another ten years. 通过协议可以延长期限。 period may be extended upon expiration (through agreement).; 延长号 [音乐] pause; 延长线 extended [extension] line