passport
n
1 official document issued by the government of a particular country, identifying the holder as a citizen of that country and entitling him to travel abroad under its protection 护照
a British passport 英国护照.
2 ~ to sth thing that enables one to achieve sth (获得某事物的)手段, 保障
The only passport to success is hard work. 通往成功的唯一途径是努力奋斗.