Difference between chancellor and president of American university?

The Word Chancellor refers to

1. Any of various officials of high rank, especially:
   1. A secretary to a monarch or noble.
   2. Chiefly British. The chief secretary of an embassy.
   3. The chief minister of state in some European countries.
2. 1. The president of certain American universities.
   2. Chiefly British. The honorary or titular head of a university.
3. Law. The presiding judge of a court of chancery or equity in some states of the United States.

However, President of American university is the one who governs the rules, regulation and policies of American university.