Any unit except special class units can change classes. Units that are Lords, Thieves, Manaketes, Ballisticians, Chameleons and Dancers cannot be reclassed. There are limitations on how many of a particular class one can have. These limitations are based on the total number of a certain class you could have plus one. For example, if in the course of the game you have recruited three paladins and one cavalier and could have recruited three more, 3 plus 3 plus 1 plus 1 is 8, so you can have 8 total cavaliers and paladins. Some classes can change into other classes, following one of three sets. This method of reclassing received mixed opinions from players. After completing Shin Monshō no Nazo on Hard difficulty or above, male sets A and B become merged.
Changing a physical unit into a magic unit will result in having very little Strength and Magic after the swap (and vice versa). If one wishes to raise such a unit, it is best to reclass them at the lowest level possible. This way, the unit will have more opportunities to raise its Magic power. That being said, one of the only usable examples of this is shown in changing the class of Draug to a Dark Mage, which is made possible by his low starting level and unusually high speed growth (60%).
Many magical units that change to physical classes will be able to gain Defense while retaining the ability to gain Resistance; however, both of the growth rates will be low.
Dracoknights are the only axe class in Male Class A, and Female Class sets.
In both games Dark Mage can only be obtained through reclassing. In Shin Monshō no Nazo, this applies to pirates as well.
Originally, Elice was the only character that could use the Aum Staff, because she was the only princess of the right class. However, several other princesses can be reclassed and use the Aum Staff.
In Shin Monshō no Nazo, it is possible to usurp the class limit through a development oversight. If you play on casual and kill units in the preparation arena, their class will open up in the reclassing screen. Reclass units to the class of the dead unit and when you start the next round, you can have over the limit. The limit still exists, though, so if you have 21/20 mounted units, if you reclass one, you won't be able to add another until you kill one, as you will have 20/20. This is the only way to have single class runs.
In Awakening, main function of reclassing is to allow the player to try out different classes as well as acquire necessary skills to make their units better. Most units have three base classes that they can change into. The Avatar and his/her children, however, can change into a Tactician and any non-special class of their gender. To change classes, a Second Seal is required. However two classes are the exception to this rule. The Dread Fighter and Bride classes require the DLC Dread Scroll and Bride's Bouquet items respectively in order to access these classes.
To reclass, a unit must be level 10 or higher in a first tier class, or at any level in a second tier class. If a unit is at least level 10 in an advanced class, they can change directly to another second-tier class; otherwise, they can only demote back to first tier. Special classes such as Dancers, Taguels or Manaketes are treated as first-tier classes until they reach Level 30. Stats are modified when reclassing and can be raised or lowered. Stat caps will also change as well as stat growths.
If a unit is at maximum level, they can "reclass" into the current class that the unit is already in, with no stat gain/loss, essentially "resetting" their level.
Children can inherit classes from their parents, giving them more than three base classes. However, if either parent has a class that the child cannot inherit due to their gender, an appropriate class is given instead. The class change gender options are specific to each character.
The Reclassing system changed slightly from the Awakening system. All characters have one additional class with their base class, including the Avatar. The Avatar's second class option is determined during the creation of the Avatar and cannot be changed once set.
With the exception of Azura's children, who inherit the Troubadour class set instead of her exclusive Songstress class, all children will inherit their fixed parent's primary and secondary class, and their variable parent's primary class. In the event where the child's primary class and the class inherited from fixed parent overlap secondary parent's classes, the child will inherit an equivalent of his secondary parent's primary class from another route (eg. Lutz will inherit Sky Knight from Beruka). Exceptions are Shrine Maiden and Troubadour classes - those gave nothing.