Now some of you may wonder why I love Regency romance. It's simple. I love the class structure of the British aristocracy. Dukes and Earls and Viscounts, oh my. I'd like to think I was a Countess in a former life. LOL. (And I know it wasn't all sunshine and lollipops for the lesser classes, but in my world they all had good jobs and decent homes and no one died from disease or pestilence.)
For those of you who'd like a primer in that world, here's a little info that may help you, in either reading, or writing it. Let's start at the top, shall we.
King & Queen -- They are the reigning Monarchs. They rule the country. You would address them as Your Majesty, Your Highness, or, Your Grace.
Prince & Princess -- Children and grandchildren of the King and Queen. You would address them as Your Highness, or, Your Grace.
Duke -- Their wives were known as Duchess. Created in 1337. These were the people who were next in line to the throne after the Prince and Princess. Their family line could be traced to the reigning Monarch. You would address them as Your Grace. During the Low and Middle Ages the Monarch would give their kinsmen land surrounding the castle. More land was gained by marrying into it. Their title would be the name of the county of which their principal holding sat, ie. Duke of Cornwall, Duke of Devonshire, etc. They all held a seat in the House of Lords in Parliament.
Marquess -- (pronounced Mar-Kwess) Their wives were known as Marchioness (pronounced Mar-Ki-o-ness or Mar-Key-o-ness) Created in 1385. These titles were created when England usurped Ireland, Scotland and Wales. Members of these aristocracies in their own country weren't in line to the throne so they couldn't become Dukes. They became Marquess instead, which is why there aren't a lot of them. You would adress them as -- my lord. They also hold a seat in the House of Lords.
Earl -- Their wives were known as Countess. Created in the 800's. You would address them as -- my lord, my lady. They were the chief royal representative in the shires (counties). Their name was usually from their place, Earl of Cory, but later, they could also use their surname if they held no land, Earl Gray. (Yes, there actually was an Earl Gray.)
Viscount -- (pronounced Vi-count) Their wives were known as Viscountess. Created 1440. Originally a Viscount was the sheriff of the shire and reported to the Earl. They mainly used their surname in their title, Viscount Hadley. They were addressed as -- my lord.
Baron -- The least of the nobility. Their wives, of course, were Baroness. Created 1066. This title was usually applied to the chief tenants of the Earl, and their land had been granted to them by the Monarch. I'm not really sure how you would address them. I think - Sir - possibly - my lord. I don't really know a whole lot about Barons.
Baronet-- Created in 1611. This is a special hereditary rank. If you remember, in Jane Austen's PERSUASION, Anne Elliot's father is a Baronet. I know you address them as Sir.
Knight -- Are NOT members of the aristocracy. They are addressed as Sir or Madam. It is an Honorary title. Sir Paul McCartney, Dame Judi Dench.
You could have as many, or as few titles, as you had ancestors. You would sometimes also lose a title if you gained another one. Say you were a Marquess and your father the Duke died, you would become the Duke. Now if you had a son, he would become the Marquess.
If you died without issue (male children) the Monarchy could usurp your title back into its fold, taking with it all land and monies you had. It would either keep it, or reissue it to someone else as was its wont.
You could also gain a title by doing some great heroic endeavor, ie. Admiral, Lord Nelson. He was just plain old Horatio Nelson when he joined the Royal Navy. After his action at Cadiz he was given the title of 1st Viscount. (He was also the Duke of Bronte but that was given to him by the King of Spain. Also, because he died without issue, his Viscountancy was taken back by the King of England, and there has never been another. However, there was a special provision for his Baronetcy that was given to his brother after his death.)
This is the list of Nelson's titles that was read at his state funeral.
The Most Noble Lord Horatio Nelson, Viscount and Baron Nelson, of the Nile and of Burnham Thorpe in the County of Norfolk, Baron Nelson of the Nile and of Hilborough in the said County, Knight of the Most Honourable Order of the Bath, Vice Admiral of the White Squadron of the Fleet, Commander in Chief of his Majesty's Ships and Vessels in the Mediterranean, Duke of Bronte in Sicily, Knight Grand Cross of the Sicilian Order of St Ferdinand and of Merit, Member of the Ottoman Order of the Crescent, Knight Grand Commander of the Order of St. Joachim.
And there you have my take on the aristocracy. Now, by all means this is not a comprehensive list or definition. This is just a cursory glance at what I've learned. Believe me, I have scads of notes and web-sites that could explain it a whole lot better. And I'll spare you from discussing precedence. It's a nightmare.