noun
Used for the formal opening ceremony of a new organization, association, or market (e.g., stock exchange).
新しい証券取引所の発会式が行われた。
The opening ceremony of the new stock exchange was held.
開会式 is a general opening ceremony for events, meetings, or conferences, while 発会式 specifically refers to the inaugural ceremony of an organization or market.
Compound of 発会 (はっかい, 'inauguration of a meeting or organization') + 式 (しき, 'ceremony').