The Collaborative International Dictionary of English v.0.48:

Operation \Op`er*a"tion\, n. [L. operatio: cf. F. op['e]ration.] 1. The act or process of operating; agency; the exertion of power, physical, mechanical, or moral. [1913 Webster] The pain and sickness caused by manna are the effects of its operation on the stomach. --Locke. [1913 Webster] Speculative painting, without the assistance of manual operation, can never attain to perfection. --Dryden. [1913 Webster] 2. The method of working; mode of action. [1913 Webster] 3. That which is operated or accomplished; an effect brought about in accordance with a definite plan; as, military or naval operations. [1913 Webster] 4. Effect produced; influence. [Obs.] [1913 Webster] The bards . . . had great operation on the vulgar. --Fuller. [1913 Webster] 5. (Math.) Something to be done; some transformation to be made upon quantities or mathematical objects, the transformation being indicated either by rules or symbols. [1913 Webster] 6. (Surg.) Any methodical action of the hand, or of the hand with instruments, on the human body, to produce a curative or remedial effect, as in amputation, etc. [1913 Webster] Calculus of operations. See under Calculus. [1913 Webster]The Collaborative International Dictionary of English v.0.48:

Calculus \Cal"cu*lus\, n.; pl. Calculi. [L, calculus. See Calculate, and Calcule.] 1. (Med.) Any solid concretion, formed in any part of the body, but most frequent in the organs that act as reservoirs, and in the passages connected with them; as, biliary calculi; urinary calculi, etc. [1913 Webster] 2. (Math.) A method of computation; any process of reasoning by the use of symbols; any branch of mathematics that may involve calculation. [1913 Webster] Barycentric calculus, a method of treating geometry by defining a point as the center of gravity of certain other points to which co["e]fficients or weights are ascribed. Calculus of functions, that branch of mathematics which treats of the forms of functions that shall satisfy given conditions. Calculus of operations, that branch of mathematical logic that treats of all operations that satisfy given conditions. Calculus of probabilities, the science that treats of the computation of the probabilities of events, or the application of numbers to chance. Calculus of variations, a branch of mathematics in which the laws of dependence which bind the variable quantities together are themselves subject to change. Differential calculus, a method of investigating mathematical questions by using the ratio of certain indefinitely small quantities called differentials. The problems are primarily of this form: to find how the change in some variable quantity alters at each instant the value of a quantity dependent upon it. Exponential calculus, that part of algebra which treats of exponents. Imaginary calculus, a method of investigating the relations of real or imaginary quantities by the use of the imaginary symbols and quantities of algebra. Integral calculus, a method which in the reverse of the differential, the primary object of which is to learn from the known ratio of the indefinitely small changes of two or more magnitudes, the relation of the magnitudes themselves, or, in other words, from having the differential of an algebraic expression to find the expression itself. [1913 Webster]