mekso operator: plus or minus with order important, (((a±b)±c)±...±z)
Strictly not "positive or negative" (if order matters, use ma'ufa'uni'u instead for that purpose). Subscript fa'u when multiple such operators (including "positive or negative" and others) are in use but are applied independently. This word is more useful and more general in mathematics than su'ijavu'u is, but is perhaps/arguably less general(ly useful) in Lojban, syntactically speaking, since not all statements have multiple occurrences of fa'u that may be linked.