first secretary (of a communist party)
Refers specifically to the top leadership position in a communist party, equivalent to party leader. Used in historical and contemporary contexts for parties such as the Chinese Communist Party or the former Soviet Communist Party.
The First Secretary of the Chinese Communist Party is the party's top leader.
During the Soviet era, the First Secretary held great power.
総書記 (general secretary) is another top party title, often used interchangeably with 第一書記 in some contexts, but 第一書記 specifically implies the first or primary secretary.
Compound of 第一 (first) and 書記 (secretary), a calque from the political terminology of communist parties.