The Dukes of the Peerage of the United Kingdom

The Dukes

In the United Kingdom there are five ranks of the peerage:

Baron is the lowest. In Scotland this is called a Lord, short for Lord in Parliament.
Viscount
Earl - this is an old saxon word. In Europe this rank is called "count", the lord in charge of a county. An earl's wife is called a countess
Marquess - A special rank higher than an earl because a marquess's land was in the Marches, the border areas that were hard to defend against attack. A marquess's wife is called a marchioness. There were not many marquesses in Scotland, and they usually spelled the title "marquis" like the French
Duke - the highest rank.

Informally Barons, Viscounts, Earls and Marquesses are called lords, and instead of their name when speaking to them, the term "my lord" is used. A Duke is never called a lord. "Your grace" is used for a Duke.

Precedence

Sorting out which peer should precede (come in front of) in a procession or other event depends on three different things:

The rank. All dukes come before all marquesses, then earls, then viscounts and finally barons.
Country the peerage was created in. All Dukes first created by the King of England come before those created by the King of Scotland. After this come Dukes of Great Britain whose titles were created between 1707 and 1801. In 1801 Ireland joined Great Britain to form the United Kingdom, so Dukes of Ireland come next, followed by Dukes of the United Kingdom.
The other types of peer follow in the same order.
         1. England
         2. Scotland
         3. Great Britain
         4. Ireland
         5. United Kingdom
The Year. Finally the order is decided on the year the title was created.