谁能用英语解释一下president

1.the elected head of a republican state
（共和国的）总统，国家主席
2.the head ofa society or council etc.
（学会的）会长
3.the head of certain colleges
（某些学院的）院长
4.[北美]the head of a university
大学校长
the head of a company,etc.
（公司等的）总裁
5.a person in charge of a meeting,council,etc.
（会议，理事会等的）主持人，主席

president
n. 1. the leader of a republic, especially the US
the president of the United States
2. the person in charge of some organizations, clubs, colleges, etc.
the president of the student's union
3. the person in char ge of a bank or a commercial organization.
the president of the world bank.

the chief executive of a republic
the officer who presides at the meetings of an organization; "address your remarks to the chairperson"
the head administrative officer of a college or university

head of state(and government) in countties that do not ha