The triangle in the Enneagram symbol alludes to the triadic nature of the types. Triads are any grouping of three numbers together.

Two general approaches appear in the Enneagram as types.

In the first approach, all nine types are grouped into three groups of three. This approach is based on the fact that 3 x 3 = 9. These triadic groupings often center around points 3, 6 and 9 as indicated by the triangle.
Examples include:

• (891), (234), (567) - best known as the doing, feeling and thinking triads or centers of intelligence
• (459), (783), (126) - best known as the withdrawn, aggressive and compliant triads or Karen Horney's triads

The second triadic approach groups two other points relative to the point of interest. In this approach, only three points are looked at instead of all nine.
Examples include:

• the points on either side of the point of interest - best known as the dominant and wing types
• connections to two other points based on the inner lines - often known as directions of integration/disintegration or stress/security points
• one point each from the doing, feeling and thinking triads - best known as the trifix