'Royal' and 'regal' are doublets — both from Latin 'regalis,' but 'royal' took the scenic French route.
Having the status of a king or queen or a member of their family; belonging to or carried out by a king or queen; of a quality or size suitable for a king or queen; impressive, magnificent.
From Old French 'roial' (modern 'royal'), from Latin 'rēgālis' meaning 'of or belonging to a king,' from 'rēx' (genitive 'rēgis'), meaning 'king,' from the PIE root *h₃reǵ- (to move in a straight line, to rule). 'Royal' is a doublet of 'regal' — both descend from Latin 'rēgālis,' but 'royal' came through French (which transformed the word phonologically), while 'regal' was borrowed directly from Latin in a later period, retaining a more Latinate form. Key roots: rēgālis (Latin: "of or pertaining