Lords of Regality are invariably addressed as 'Lord Placename', whilst feudal barons are addressed as 'Baron of Placename' or 'Placename'.
Regalities were all but abolished by Act of Parliament in 1747, following the Jacobite Uprising. A feudal barony no longer carries any political power as such, although the Abolition of Feudal Tenure etc. (Scotland) Act 2000 has preserved the baronies themselves, and the quality, precedence and heraldic rights pertaining to these baronies.
A female feudal baron is usually referred to as 'Lady Placename'. The wife of a Lord receives the courtesy title 'Lady Placename', but the husband of a Lady is just plain Mr. Surname'.
Lords of regality and feudal barons are not to be confused with a manorial lordship.
Scottish titles, in order of precedence, are as follows: Duke, Marquis, Earl, Viscount, Lord (of Parliament), Baronet, Knight, feudal Baron, Clan Chief, Esquire/Gentleman.