A class (vocation/job) is a specific role classification given to party characters in the Dragon Quest series.
Dragon Quest III
In Dragon Quest III, the player begins with only the Hero and can choose up to three other party members from Ruida's Tavern. These characters have different classes and it is up to the player to decide what party members they want for their teams. Each of the jobs had its own strengths and weaknesses which allowed the player to build a team based on their own preferences. At any time, the player can leave and replace party members here. The party members who are kept in the tavern with whatever stats and equipment that they gained during their travels.
About halfway through the game, the player will reach the Temple of Dharma, which will allow the player to change the jobs of their team without going to Ruida's Tavern. For example, a Warrior can become a Mage at the Temple. The Hero cannot change classes. There is also a Sage class that can only be accessed through the Temple. However, it can only be acquired in one of two ways. The Book of Satori can be found in the Tower of Garuna. The other way is to raise a Goof-off to level 20 and heading to the Temple of Dharma.
Becoming a new class has its downside. The changing party member loses half their stats and their level returns to 1. This can be beneficial to a player because this means that a Thief can become a Warrior and have half the gained agility.
Dragon Quest VI
Unlike in Dragon Quest III, this game starts with nine available classes. Each of the classes has eight tiers (or levels) that can be achieved through battling monsters. Through mastering the available classes, more classes can be accessed. For example, by mastering the warrior and the Fighter classes will allow the character to become a Battlemaster. Every class has their strengths, weaknesses and skills all their own. The skills transfer from class to class.
Dragon Quest VII
The class system remains mostly unchanged from the previous game. In the beginning human classes, there are, what are known as, hybrid abilities. Hybrid abilities combines two classes and creates an ability. For this to happen, a character must first be matured in two classes. For example, a party member who wants to know Sword Dance must first become a tier five Warrior and then become a tier five Dancer to learn the skill. In addition, there are now three levels of human classes: the beginner classes which are available from the start, the intermediate classes which combines two or three beginners classes, and the advanced classes which combine two intermediate classes.
Finally, party members can also become monsters by using Monster Hearts. By putting a monster heart in their inventory and going to the Temple of Dharma, they can become that monster. Monster classes work just like human classes. However, after the eighth tier, the party member begins to look like the monster they have become, including changing the sprite of the character. Monster classes have much more combinations than human classes.
In all, there are over fifty classes that a single character can become in this game.
Dragon Quest IX
Dragon Quest IX has a class system which is similar to the one in Dragon Quest III, where the player may create additional party members and add them to the party. This can be done at the Quester's Rest located in Stornway, by speaking to Patty the party planner. Party members created do not play any significant part in the plot.
Classes can be changed at the Alltrades Abbey, after the player has rescued Abbot Jack. There is not minimum level limit for changing classes. Classes can be changed as often as desired. One notable difference from past games is that spells are no longer carried over between class changes. A character must be a specific class to use that classes spells. Skills do carry over, and there are also methods for utilizing each weapon type with all classes.
Additional vocations must be unlocked by doing quests before the player can switch to them. Notably, the Sage class is accessible only later in the game, but includes a specific ability, Jack's Knack, which allows the party members to change class at any time and place.
There are a total of 12 classes available in Dragon Quest IX.