WIZARD

The Realms of Magic:

The Six Realms of Magic subsume those spells which...

Elementalism:  manipulate, create, draw upon, or block out one or more of the 
four alchemical elements of air, earth, fire, and water.

Enchantment:  embed magical power within a creature, object, place, or 
substance or cause a fundamental change in the form or nature of the target of 
the magic.

Illusion:  disguise, distort, hide, or alter the appearance or the essential substance 
of reality through manipulation of space, time, and/or thought.

Lore:  discover, reveal, and communicate knowledge and information.

Necromancy:  deal with the nature of death, darkness, life force, and the undead.

Sorcery:  contact, create, conjure, and control other creatures, quasi-real magical 
constructs, and 'pure' magical energies and forces for offensive and defensive 
applications in combat.

All Wizard classes have one Realm of Magic as their Primary Field of Study 
(FOS), allowing them to master the most potent spells within their area of 
expertise.  Wizards can also learn spells from outside their area, though they will 
never equal the skill in other areas as they possess within their own Primary FOS, 
save for Universal Magic and Metamagic, which all Wizards count as equivalent 
to a Primary FOS.

A Wizard's knowledge of other Realms of Magic is quantified as being a Minor 
or Major Field of Study (FOS):

Minor Field of Study:  Spells in this Realm are considered to be double their 
normal level, with double the normal casting time.  A Wizard has only half the 
normal chance to know spells in a Minor FOS, and they take effect as if the 
caster was only half his or her actual level (rounded down).  Only spells up to 4th 
level (doubled to 8th level) can be learned in a Minor FOS.

Major Field of Study:  Spells in this Realm are cast at their normal level and with 
their normal casting time, with the normal chance to learn spells in a Major FOS.  
They still take effect at only half the caster's actual level (rounded down), and the 
caster is still limited to using spells of 4th level and below.

STANDARD WIZARD ABILITIES:

Wizards have the option to leave any or all 'spell slots' open rather than 
memorizing spells immediately after rest.  Such spell slots can then be used later 
in the day by reading and memorizing a particular spell from the Sorcerer's 
spellbooks at the time it is needed (requiring the normal 10 minutes per spell 
level) and then casting it, allowing for greater flexibility but leaving him or her 
without a prememorized, ready-to-cast spell in that slot.

Wizards receive bonus spells (and/or have a spell failure chance) based on their 
Intelligence score as a Priest would for a high Wisdom score; these bonus spells 
must be selected from their Primary FOS.

Wizards can research and create spells and magical items, but only within their 
Primary FOS.

Wizards gain the ability to scribe spells onto scrolls beginning at 6th level, 
provided appropriate spell inks can be bought or manufactured and the 
Calligraphy proficiency is known.  They can also begin to brew magical potions 
at this level if the Alchemy and Brewing proficiencies are known.

Obviously, there is more information to come in this arena/system of magic, 
which I will send along as I complete it, but you could use these general 
parameters to simply quantify things along the lines of standard AD&D schools 
of magic.