Spontaneous, Memorized and Known Spells

Before a spellcaster can use a spell, he or she must have the spell firmly fixed in mind, or must have access to the spell in a magic item. Members of a few classes have a limited list of spells they know that are always fixed in their mind and can be cast spontaneously. The same thing is true of many magic using monsters.

Other spellcasters, such as clerics and wizards can know a far greater number of spells but must undergo a process of memorizing spells from their list of known spells in order to fix them in mind and cast them spontaneously. These casters can still cast spells that they haven't memorized, as long as they know the spell, and undergo a process of preparing the spell first. The process and cost of preparing a spell varies for different classes, as detailed in their descriptions.

In every case, the number of spells a caster can have fixed in mind at any given time depends on the character's level.