An adverb meaning 'mainly' or 'primarily'—indicates that the majority pertains to a certain characteristic or use. Common in everyday speech and writing; more colloquial than '主として'.
この地域は主に農業で生計を立てている。
This region mainly makes a living through agriculture.
会議は主に次の三つの項目について話し合われた。
The meeting mainly discussed the following three items.
彼の仕事は主に海外向けの営業だ。
His job is primarily sales aimed at overseas markets.