1. A person or thing being discussed, considered, or acted upon:
* "The subject of the conversation was the upcoming election."
* "The artist chose a beautiful landscape as the subject of her painting."
* "The doctor examined the patient's subject, a small mole on her arm."
2. A person under the rule of a sovereign or state:
* "The king's subjects were loyal to their monarch."
* "The citizens of a country are its subjects."
3. A branch of study or knowledge:
* "Mathematics is my favorite subject."
* "The professor is an expert in the subject of ancient history."
4. In grammar, the noun or pronoun that performs the action of a verb:
* "The cat (subject) chased the mouse (object)."
* "She (subject) wrote a letter (object)."
5. In photography, the main object or person being photographed:
* "The subject of the photo was a stunning sunset."
* "The photographer asked the subject to smile for the camera."
6. In medicine, a person participating in a medical experiment or study:
* "The subjects in the clinical trial were randomly assigned to different treatment groups."
It's important to consider the context to understand the meaning of "subject" in a particular sentence.