On grammatical class:

bi'u
discursive: newly introduced information - previously introduced information.
jo'a
discursive: metalinguistic affirmer.
kau
discursive: marks word serving as focus of indirect question: "I know WHO went to the store".
li'o
discursive: omitted text (quoted material).
na'i
discursive: metalinguistic negator.
pau
discursive: optional question premarker.
sa'a
discursive: material inserted by editor/narrator (bracketed text).
ta'u
discursive: expanding the tanru - making a tanru.
bi'a
emphasis indicator; indicates the previous word is especially emphasized; equivalent to {ba'e} but in UI
li'oi
marks word as being optional, i.e. the bridi would still be both grammatical AND reflect the speakers opinion/intention would the marked construct be left out
zi'a
nonce-word indicator; indicates previous word is nonce-creation and may be nonstandard; equivalent to {za'e} but in selma'o UI