賀がする

が

す

る

Meanings

1

suru verb (special), transitive verb

Formal, often used in set phrases such as 新年を賀する (celebrate the New Year) or 就任を賀する (congratulate on an appointment).

て

、

同どう

僚りょう

が

パーティー

を

開ひら

い

た

。

His colleagues threw a party to congratulate him on his promotion.

祝いわう
祝う is the common, everyday verb for celebrating or congratulating. 賀する is more formal and often used in official or written contexts.

From the kanji 賀 (congratulation) combined with the verbalizer する. The reading が is the on'yomi of the kanji.