omittable text; one sense of ‘[]’ square brackets (bracketed text).
Can be used with quotations. See also sa'a for editor-inserted material, and na'i'a of UI3b, which can be used like po'o except to express optionality, rather than uniqueness. See also li'oi, which is very similar to la'i'a but also claims that the result would still be grammatical if the construct li'oi applies to is removed, whereas la'i'a does not necessarily make this claim.