noun

• the subject matter of a conversation or discussion
  "he didn't want to discuss that subject"
• something (a person or object or scene) selected by an artist or photographer for graphic representation
  "a moving picture of a train is more dramatic than a still picture of the same subject"
• a branch of knowledge
  "in what discipline is his doctorate?"
• some situation or event that is thought about
  "he kept drifting off the topic"

verb

• cause to experience or suffer or make liable or vulnerable to
  "He subjected me to his awful poetry"
• make accountable for
  "He did not want to subject himself to the judgments of his superiors"
• make subservient; force to submit or subdue
• refer for judgment or consideration
  "The lawyers submitted the material to the court"