• 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

賀 combines the 貝 radical (shell/money, symbolizing value) with 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.