An Ajah is one of the seven groups within the Tower. Each Ajah has its own rules, traditions, customs and often secret weaves (NS, Ch. 23), known only to the members. They each have their own purpose and tend to attract people with an interest in that area. Accepted are also moulded and guided towards the most appropriate Ajah. As such, there is often a stereotype associated with each.
In the Age of Legends, there were no Ajah. Instead, ajah, informal associations of Aes Sedai existed, By 200AB, this had changed to Ajah (TWoRJTWoT, Ch. 9). In 47AB, when the Tower was in the process of formation, twelve women are listed, plus several others, as sitting "for their ajah if they can still be called so" (TWoRJTWoT, Ch. 9) By 98AB, an Amyrlin Seat had been chosen with seven women advising her (TWoRJTWoT, Ch. 9). The fact that twelve women (one of whom later became Amyrlin) were narrowed down to seven advisers, plus that those who did not submit willingly were forced into doing so (TWoRJTWoT, Ch. 9) suggests that the transition to Ajah was based on seven independent groups forming the White Tower.
- Main article: Blue Ajah
The Blue Ajah concerns itself with causes. It is the smallest after the White.
- Main article: Brown Ajah
The Brown Ajah concerns itself with knowledge.
- Main article: Gray Ajah
The Gray Ajah concerns itself with mediation. It is the third largest Ajah.
- Main article: Green Ajah
The Green Ajah concerns itself with being prepared for the Last Battle. It is the second largest Ajah.
- Main article: Red Ajah
- Main article: White Ajah
The White Ajah concerns itself with logic. It is the smallest Ajah.
- Main article: Yellow Ajah
The Yellow Ajah concerns itself with Healing. It is the third smallest Ajah.
Blue and Red opposed each other almost automatically in the Hall and are seldom friendly outside, and Green and Blue almost always support each other (NS, Ch. 9, TGH, Ch. 4). Red and Green are similarly usually in opposition (TGH, Ch. 4). Other relationships may be more complex, for example, Brown supports White against Blue, but Blue against Yellow (NS, Ch. 9). The Yellow and Blue have had a tense relationship for a hundred years (NS, Ch. 14).