请帖
qǐng tiě · HSK 7
invitation card
💌 请帖 = 请 (invite) + 帖 (card/note) — the card that invites you
请 carries the 'please/invite' sense (same 请 as 请客, to treat a guest); 帖 is a written slip or card. Put together, a 请帖 is the formal slip that does the inviting — a written invitation.
请 — speech radical 讠 + 青 (qīng, blue/green)
请 is a semantic-phonetic compound. The speech radical 讠 (言) signals a meaning related to speaking, while 青 (qīng) supplies the sound. Originally it meant 'to ask' or 'request' through speech, and later extended to the polite 'please' and 'to invite'.