Doctor (noun)

1. A person who is qualified to treat people who are sick or injured.
2. A person who has earned a highest degree in a specified field of study.
3. A person who gives medical treatment.
4. A person who mends or repairs.
5. A person who makes changes or gives advice.

Origin:

Middle english doctour, from old french, from late latin doctus learned, from latin doctus, past participle of docēre to teach.

Examples:

1. She went to the doctor for a checkup.
2. He is a doctor of philosophy.
3. The doctor prescribed medicine for the illness.
4. The mechanic is a doctor of engines.
5. The editor acted as a doctor for the manuscript.