高考英语词汇解析：on board
on board是介词还是副词
on board 既可以用作介词，也可以用作副词。
1. 用作副词时，表示“在船上”。如：
Have the passengers gone on board? 旅客都已上船了吗?
As soon as I’m on board, I always feel sick. 我一上船就想呕。
2. on board 用作介词时，其后可直接跟表示车、船、飞机的名词。如：
He went on board the train just now. 他刚上火车。
Mr Smith is on board one of those ships. 史密斯先生在其中的一条船上。
There were ten people on board the plane. 当时飞机上有十个人。
