On grammatical class:

bu'u
location tense relation/direction; coincident with/at the same place as; space equivalent of ca.
ne'a
location tense relation/direction; approximating/next to ...
ne'i
location tense relation/direction; within/inside of/into ...
pa'o
location tense relation/direction; transfixing/passing through ...
re'o
location tense relation/direction; adjacent to/touching/contacting ...
te'e
location tense relation/direction; edged by/edging up to ...