机要的英文：
confidential

参考例句：

Is the plane leaving?
飞机要起飞了吗?

How long will it take to have this radio fixed?
修理这收音机要多久?

She had a sinister foreboding that the plane would crash.
她有个不祥的预感,飞机要失事.

Should I request a transfer from the bus driver?
我要向司机要换车证吗?

The pilot told us to buckle our seat belts because the plane was about to land.
驾驶员叫我们扣好安全带，因为飞机要降落了。

The indicator on a car is a flashing light which tells you that the driver is going to turn.
汽车上的指示灯是种闪光的灯，它告诉你司机要拐弯儿。

confidential是什么意思：
adj. 秘密的；信任或亲密的；担任机密工作的

confidentiality of contracts
合同的保密性

He has been on confidential missions to Berlin.
他前往柏林执行秘密任务。

He told me the confidential information.
他向我透露了这个秘密的信息。

Don't be too confidential with strangers.
不要过份相信陌生人。

She is a confidential secretary of Mr. Smith.
她是史密斯先生的一个机要秘书。