This is the 115th most frequent Japanese word.
主催
Sponsorship; hosting; organizing.
In this sentence, '主催者' (organizer) derived from '主催' indicates a person or party responsible for organizing an event.
主催者としての責任を果たします。
I will fulfill my responsibility as an organizer.
The word '主催' is used to indicate the organizing or hosting entity of an event.
このイベントは市が主催しています。
This event is hosted by the city.
Here, '主催' is used as a verb to describe the action of organizing or hosting conferences.