It seems that there are as many different terms and definitions as there are teachers of the enneagram. To keep things less confusing, here is a definition of the terms as I use them on this site.
Type: the 9 types of the Enneagram
Subtype: Also known as Instinctual Variants. Each type is one of 3 subtypes. Everyone has all 3 subtypes in different orders.
- SX: Sexual, One-to-One
- SO: Social
- SP: Self-Preservation
Stacking: The order of dominance is called stacking. There are 9 stackings.
Triads: These are sometimes called groups but on this site I will refer to all of them as triads. There are a total of 9 triads.
Hornevian Triad
Harmonic Triad
Psychological Triad