• 年賀状ねんがじょう — New Year’s card
• 祝賀会しゅくがかい — celebration party
• 賀詞がし — congratulatory words
• 賀正がしょう — New Year's greeting (formal)
• 参賀さんが — imperial New Year's visit
• 来賀らいが — paying a celebratory visit

“賀” includes the radical 貝 (shell/money), indicating value, and phonetic 加. It suggests offering something valuable with joy, such as words or gifts of celebration. It appears mostly in set phrases and formal writing.

年賀状ねんがじょうを 送おくりました。
I sent a New Year’s card.

賀詞がしを 述のべる機会きかいを 得えました。
I had the chance to express congratulatory words.

The on-yomi ガ is used in all words featuring 賀. You’ll rarely see this character used alone in modern writing, but it's essential in formal or ceremonial expressions.