Regal means fit for a monarch, and grand in bearing. A regal manner, regal splendour, look regal.
It describes the impression of royalty rather than the fact of it — a regal woman need not be a queen — which is why it works as a compliment for bearing and for décor. Royal describes the fact and regal the manner. Note regally; and that regal, royal and real are the same Latin word, rex, arriving by three routes, which is why they mean such different things.
1adjectiveregalFit for a monarch, and grand in bearing.
“She walked into the hall with a regal air, her head held high.”
synonyms: majestic, kingly
regal is a quality of kingliness.
Latin regalis comes from rex, a king. Royal came through French and real through Spanish, so regal, royal and the Spanish real are all the same king.
Proto-Indo-European
*h₃reǵ-
Latin
rēgālis — royal, kingly
Old French
regal — regal, royal
Middle English
regal
English, today
regal
Built from
From Middle English regal, from Old French regal (“regal, royal”), from Latin rēgālis (“royal, kingly”), from rex (“king”); also regere (“to rule”). a doublet of royal and real and ariary and riyal. Cognate with Spanish real, Italian reale, Catalan reial.
Etymology from Wiktionary, CC BY-SA