drowsiness       
noun [ U ] uk/ˈdraʊ.zi.nəs/ us/ˈdraʊ.zi.nəs/
 困倦;睡意
a tired state, between sleeping and being awake
  Seasickness medication often causes drowsiness. 晕船药常让人感到困倦。 
 There's no test to measure driver drowsiness the way that breathalizers check for alcohol. 目前还没有检查可以像酒精检测仪检查酒精含量那样来测量驾驶员的困倦程度。 
 See: drowsy
 - More examples
 - Side effects of the drug include headache, dizziness, drowsiness or insomnia.
 - According to the National Traffic Safety Administration, drowsiness causes 100,000 vehicle crashes a year.
 - Nutrition experts say that daytime drowsiness is the most common complaint they hear.
 - Certain antihistamines can cause drowsiness and shouldn't be used while driving or doing other tasks that require alertness.