名词形式是sign，意思是：符号，标记，迹象等，例如：
1、The involvement of the foreign ministers was itself a sign of progress.外交部长的介入本身就是取得进展的一个标志。
2、Pictures of road signs are matched with their Highway Code meanings.道路标志图是同公用通道法规一致的。
3、Go straight through that door under the EXIT sign.从“安全出口”标志下的那道门直穿过去。
