Tritype is trademarked by Enneagram Explorations (Katherine Chernick Fauvre and David Fauvre). It is sometimes confused with the trifix concept of Oscar Ichazo because it was originally called trifix by the Fauvres' until it was discovered that the Fauvres' application of the trifix concept was something different than Ichazo's.
In a tritype, an individual has a dominant type in each of the centers of intelligence (a body-based type, a heart-based type, and a head-based typed).
As an example, if a person identifies as a type 1, then type 1 is his or her dominant body-based type. Suppose, of the heart-based types (2, 3, and 4), the person identifies most closely with type 4. Type 4 becomes his or her dominant heart-based type. Of the head-based types (5, 6, and 7), the person identifies most with type 6. Type 6 is then his or her dominant head-based type.
From this example, types 1, 4, and 6 are part of the person's tritype. There is also a preferential order to the types that needs to be determined. Type 1 is already identified as the person's primary type. Suppose this person identifies more with type 6 than with type 4. The tritype is then 1-6-4. This not only indicates the dominant type in each center but also the preferred order of the tritypes.
With tritype archetypes, the preferential ordering is disregarded in describing the 27 possible archetypes. For example, the 1-2-5, 2-5-1, and 5-1-2 tritypes would all fall under the same archetype - The Mentor.
A variation of the tritype concept has appeared outside of the Fauvres' writings where the dominant type and wing are used for each center. For example, instead of 5-3-1, an individual may also include the wings with each type resulting in the 5w4-3w2-1w9 tritype with wings.