It is becoming more popular on American talk shows to say "calculus" instead of "calculation." To my mind, calculus is either a branch of Mathematics or a stone like in the gall bladder. Any comments?
Calculus in the sense of "calculation" has appeared in editions of Merriam-Webster's Collegiate Dictionary from the first one (published in 1898). In fact, this is the only mathematical definition of calculus in that dictionary:
Any process of reasoning by the use of symbols ; any branch of mathematics that may involve calculation.
However, the subsequent rise of differential and integral calculus altered the dictionary's definitions considerably. The Third Collegiate (1916) has these relevant definitions for calculus:
2 A method of computation ; esp., a branch of higher mathematics (differential and integral calculus) by which problems involving motion or constant variation are solved. 3 A book containing the principles of this science.
By the time the Seventh Collegiate (1963) appeared, the "higher mathematics" sense of calculus appeared to be complete. Here are that dictionary's relevant definitions of calculus:
2 archaic : CALCULATION 3 a : a method of computation or calculation in a special symbolic notation b : the mathematical methods comprising differential and integral calculus
So when did Merriam-Webster remove the "archaic" label from calculus in the sense of "CALCULATION"? It happened in 1983, with the release of the Ninth Collegiate:
calculus (1666) 1 a : a method of computation or calculation in a special notation (as of logic or symbolic logic) b : the mathematical methods comprising differential and integral calculus 2 : CALCULATION
The only significant alteration to the entry for calculus to occur since the Ninth Collegiate was the addition in the Tenth Edition (1993) of this new and more general sense of the word:
4 : a system or arrangement of intricate or interrelated parts
So from 1993 forward, Merriam-Webster has acknowledged the use of calculus in such phrases as "a calculus of communicating systems."
It is hardly surprising that people who spent significant time speaking English between 1963 and 1983 should have a sense that using calculus to mean "calculation" is either old-fashioned (if they remember "archaic" instances of that usage from those years) or newfangled (if they don't). But calculus-as-calculation has a long history of usage in English, as well as lots of current usage; and in business meetings across the land, the fact that "calculus" sounds more impressive than "calculation" almost guarantees that its popularity in coming years will grow rather than diminish.