the method or process of computation with figures: the most elementary branch of mathematics.
2.
Also called higher arithmetic, theoretical arithmetic. the theory of numbers; the study of the divisibility of whole numbers, the remainders after division, etc.
1200-50; < Latinarithmētica, feminine singular of arithmēticus < Greekarithmētikḗ (téchnē) (art, skill) of numbers, equivalent to arithmé(ein) to reckon + -t(o)- verbal adjective + -ikḗ-ic; replacing Middle Englisharsmet(r)ike < Old Frencharismetique < Medieval Latinarismētica, with s for Late Greekth
mid-13c., arsmetike, from Old French arsmetique (12c.), from Latin arithmetica, from Greek arithmetike (tekhne) "(the) counting (art)," fem. of arithmetikos "of or for reckoning, arithmetical," from arithmos "number, counting, amount," from PIE root *re(i)- "to reason, count" (cf. Old English, Old High German rim "number;" Old Irish rim "number," dorimu "I count;" Latin ritus "religious custom;" see read).
Originally in English also arsmetrik, on folk etymology from Medieval Latin ars metrica; spelling corrected early 16c. Replaced native tælcræft, literally "tell-craft."
(ə-rĭth'mĭ-tĭk) The mathematics of integers, rational numbers, real numbers, or complex numbers under the operations of addition, subtraction, multiplication, and division.