Perhaps, then, an open mouth is more a sign of some impending change of state rather than a statement of tiredness itself; awake to asleep or vice versa.

如此说来，也许张嘴打哈欠只是一种即将改变状态的信号，而不是疲倦本身的表现；由醒到睡，反之亦然。

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The first sign of oral cancer is often a tiny white or red spot in the mouth, but the disease can be detected before a sore appears.

口腔癌的最初症状通常是在口腔内出现一小块白色或红色的斑点，可是，在疮口出现以前这种病是能检测出的。

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Another nonverbal sign of lying is a forced smile, which generally involves only the muscles of the mouth and not the rest of the face.

另一个说谎的征兆是强挤出来的笑容，这种笑容只是调动了嘴部的肌肉而不是整个脸部的肌肉。

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Norman Betchley, who had a nil by mouth sign above his bed, choked and died after taking the pill in 2009.

BBC: Norman Betchley

The family said these were removed after a few days, but when they next visited there was a nil-by-mouth sign above her bed and they also found faeces under her finger nails.

BBC: Essex

Speaking to the BBC, Mr Betchley's son, Stuart, said there had been an A4 "nil-by-mouth" sign on the wall above his father's hospital bed.

BBC: Norman Betchley