doctor, physician, surgeon, dentist
这些名词都有医生之意。
doctor :普通用词，泛指各科医生，即一切有行医资格的人。
He would not dream of becoming a doctor.（他做梦也没想到要当大夫。）
physician :指医院的内科医生。
In case of diabetes, physicians advise against the use of sugar.（对于糖尿病患者, 医生告诫他们不要吃糖。）
surgeon :指专修外科或专修人体某个部分的外科专科医生，这种医生一般需对患者进行手术治疗。
The surgeon is now operating.（外科医生正在做手术。）
dentist :指专门从事治牙的医生。
I have got toothache, so I must go to a dentist.（我牙疼, 必须去看牙医。）