noun
(dated, countable) Calculation; computation.
(countable, mathematics) Any formal system in which symbolic expressions are manipulated according to fixed rules.
(uncountable, often definite, the calculus) Differential calculus and integral calculus considered as a single subject.
(countable, medicine) A stony concretion that forms in a bodily organ.
(uncountable, dentistry) Deposits of calcium phosphate salts on teeth.
(countable) A decision-making method, especially one appropriate for a specialised realm.