Mr. Ma wrote a letter to the headmaster.

Main referential meaning

Collins advanced English-Chinese dictionary of dual-solution learning

1

Primary; Most important; foremost

The main meaning is the first place in order of importance.

Collocation mode ADJ n

This is the main reason why I changed my mind.

This is the main reason why I changed my mind.

... the country's main source of foreign exchange earnings ...

The country's main source of foreign exchange income.

They must be most concerned about winning the next general election.

They must be most concerned about winning the next general election.

2

N-COUNT (primary and secondary school) principal; (British) president of a university, dean of a college.

The headmaster of a school, or the headmaster of a college in Britain, is the head of a school or college.

Donald King is the principal of Dartmouth High School.

Donald King is the headmaster of Dartmouth Middle School.