a physical or mental condition that is not normal or healthy紊乱；失调；疾病
[count]
A dermatologist treats disorders [=diseases] of the skin.
皮肤科医生治疗皮肤病
an eating disorder
进食障碍
a disorder of the blood = a blood disorder
血液疾病
[noncount]
Millions of people suffer from some form of personality/mental disorder.
数以百万计的人都患有某种形式的人格障碍/精神疾病。