abbaco
n.— «In marked contrast to the Jesuits, Piarists taught in the vernacular, not Latin, and over philosophical mathematics they favoured “abbaco”, or mercantile arithmetic.» —“Sins of the fathers” by Miranda France Guardian (U.K.) May 22, 2004. (source: Double-Tongued Dictionary)
Further reading
If you speak a second or third language, you may remember the first time you dreamed in that new tongue. But does this milestone mean you’re actually fluent? And a couple’s dispute over the word regret: Say you wish you’d been able...