a statement by a doctor that sb has been ill and unable to work （关於疾病或残疾的）医学证明书◆If you are absent for longer than five days, we may require you to produce a medical certificate. 如果你缺席五天以上，我们可以要求你出示医学证明书。
a statement by a doctor that sb is in good health and can do a particular job 健康证明书◆Pilots must hold a valid medical certificate. 飞行员必须持有有效的健康证明书。