The common folk serve the barons, who serve the earls, who serve the dukes, who serve the king. This is the most basic list of the ranks of nobility that exists.
When addressing a person you do not know: an adult male is "sir," an adult female who is wed is "madam," and a young adult female is "miss."
A knight's title is "ser." When uncertain about any member of nobility's rank, "lord" and "lady" are acceptable. Otherwise, their rank is their title, save in very specific cases, such as council members and knights of landed nobility.
The nobility of the highest tier, linked to the King and His Majesty's blood.
The King and Queen
Joint rulers of equal power, one typically taking a second seat to the other to avoid conflicts. This position has been held by the Kinguard family since before they held the name, and the current King and Queen are named Mansfeld and Victoria. They have three living children.
The Crown-Prince and Crown-Princess
Second to the royal father and mother figures, he or she is the first born or the most fit to ascend to his or her parents' throne. Currently, the heir to the throne of Saldecia is Prince Marc, who is crippled and sickly, and his physician from Highpoint is not certain he'll live long enough to take the throne. The heir holds the technical title of duke or duchess, and manages the duchy of Axevrai as training for taking the crown.
Prince and Princess
Right below the heir are his or her siblings, and possibly children, nieces, or nephews. Currently, there is one prince and one young princess, named Brahm and Camille respectively. Of the two, Brahm is expected to inherit, but the people favor Camille for her health and wisdom. Like the heir, princes and princesses also hold duke and duchess titles.
Nobility of the lower tier, by birthright or royal decree. The higher ranks have been in the same family for many generations.
The Dukes, who rule the Duchies of Saldecla, are the highest tier of noble below the royalty. There are a total of eight dukes, who share power with their spouses. These dukes and duchesses form a council below the king, working together to keep the country in balance and prosperous. Each duke must follow rigid rules in order to retain his position. Their heirs hold the title of earl or earless and manage the area immediately surrounding the ducal capitals to practice for their ducal duties.
The Earls, who rule the counties, answer to the Dukes and maintain order of command. Each manages between three and seven baronies, and serve the dukes directly. There are typically three earls under each duke, and they have limited law-making power. Dukes set out rigid rules for them to follow in their administration. Heirs for earls function as barons.
The Barons, who rule the cities and townships, answer to the Earls. They have little power other than land management, but earn wealth through a portion of taxes paid. Heirs of the barons often act as knights or ladies and keep the peace within the household and their parents' lands.
The Knights and Ladies, children of other nobility, or those who have landed their titles, answer to all the above. Most knights and ladies serve Duke Achille or the King, though it isn't unusual for knights to also serve other troubled area on the orders of their own lords.
The pseudo-nobility, individuals of substantial enough influence and power to command status. This includes Merchant-Lords, Guildmasters, or even Stewards. They are not land-owners, but are well-respected for their success.