The Latin adverbs plus and minus mean "more" and "less". They are also neuter compatative adjectives. In all languages I know these two words are used for mathematical the operations of addition and subtraction when reading formulas out loud. I guess it was also so in Latin at some point.
When did these words acquire this meaning? Do we know if it happened first in Latin or in some other language? What is known about how and why these Latin adverbs were chosen for this purpose?
The following extract from the Oxford English Dictionary, art. "plus", is perhaps of interest:
The prepositional use (sense A. 1), from which all the other English uses developed, did not exist in Latin of any period. It probably originated in the commercial language of the Middle Ages (see discussion at minus prep., n., adv., and adj.). The signs + and − occur for the first time in print in J. Widmann Behende vnd Hubsche Rechenung auff allen Kauffmanschafft (1489), a treatise on commercial arithmetic; but while Widmann refers to the latter as minus , the former is said to stand for mer (i.e. mehr ): ‘was − ist, das ist minus, und das + ist das mer’. So far as is known, English examples of plus do not occur as early as those of minus .
In a somewhat different sense, Latin plus and minus had been employed in 1202 by Leonardo Pisano (also known as Leonardo Fibonacci) for the excess and deficiency in the results of the two suppositions in the Rule of Double Position (see position n. 2); see further M. Cantor Vorlesungen über Geschichte der Mathematik (ed. 2, 1899) II. 230–1.
As to the origin of the symbol +, the most likely is that it originated as one of the MS abbreviations of the Latin et ‘and’ (see F. Cajori Hist. Math. Notations (1928) I. iii. 229–39).
Instances of the written word (as opposed to the symbol) are rare before the 17th cent.
The article "minus" says more or less the same.
