Dual-classing is a process that a player can apply during character creation. A dual-classed character represents the ideal of a particular combination of classes - the ideal warrior/mage, the ideal priest/thief, et cetera. For the most part, a dual-classed character is rolled up and leveled like any other character - but with a few key differences.
A character is only eligible to become a dual-classed character at first level. This decision cannot be made later on in his career after attaining additional hit dice, and it cannot be undone once selected. The path of a dual-classed character is a long and difficult one, requiring a lifetime of dedication to perfect.
When creating a dual-classed character, the player must select a demi-human race. For the purposes of dual-classing, a demi-human race is any humanoid race that possesses a subtype other than "Human" (for example, elves, dwarves, gnomes, halfling