|System Reference Document v3.5|
There are 11 standard character classes defined in the SRD. They are:
A character may add new classes as he or she progresses in level, thus becoming a multiclass character. The class abilities from a character’s different classes combine to determine a multiclass character’s overall abilities. Multiclassing improves a character’s versatility at the expense of focus.
As a general rule, the abilities of a multiclass character are the sum of the abilities of each of the character’s classes.
“Class level” is a character’s level in a particular class. For a character whose levels are all in the same class, character level and class level are the same.
If a skill is not a class skill for any of a multiclass character’s classes, the maximum rank for that skill is one-half the maximum for a class skill.
Class Features: A multiclass character gets all the class features of all his or her classes but must also suffer the consequences of the special restrictions of all his or her classes. (Exception: A character who acquires the barbarian class does not become illiterate.)
In the special case of turning undead, both clerics and experienced paladins have the same ability. If the character’s paladin level is 4th or higher, her effective turning level is her cleric level plus her paladin level minus 3.
In the special case of uncanny dodge, both experienced barbarians and experienced rogues have the same ability. When a barbarian/rogue would gain uncanny dodge a second time (for her second class), she instead gains improved uncanny dodge, if she does not already have it. Her barbarian and rogue levels stack to determine the rogue level an attacker needs to flank her.
In the special case of obtaining a familiar, both wizards and sorcerers have the same ability. A sorcerer/wizard stacks his sorcerer and wizard levels to determine the familiar’s natural armor, Intelligence score, and special abilities.
Spells: The character gains spells from all of his or her spellcasting classes and keeps a separate spell list for each class. If a spell’s effect is based on the class level of the caster, the player must keep track of which class’s spell list the character is casting the spell from.