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.
Also, ar⋅ith⋅met⋅i⋅cal.of or pertaining to arithmetic.
Origin: 1200–50; < L arithmētica, fem. sing. of arithmēticus < Gk arithmētik (téchnē) (art, skill) of numbers, equiv. to arithmé(ein) to reckon + -t(o)- verbal adj. + -ik-ic; r. ME arsmet(r)ike < OF arismetique < ML arismētica, with s for LGk th
The mathematics of integers, rational numbers, real numbers, or complex numbers under addition, subtraction, multiplication, and division.
Archaic A book on this kind of mathematics.
adj.
ar·ith·met·ic (ār'ĭth-mět'ĭk) also ar'ith·met'i·cal (ār'ĭth-mět'ĭ-kəl)
Of or relating to arithmetic.
Changing according to an arithmetic progression: The increase in the food supply is arithmetic.
[Middle English arsmetike, from Old French arismetique, from Medieval Latin arismetica, alteration of Latin arithmētica, from Greek arithmētikē (tekhnē), (art) of counting, feminine of arithmētikos, from arithmein, to count, from arithmos, number; see ar- in Indo-European roots.] ar'ith·met'i·cal·ly adv., a·rith'me·ti'cian (-tĭsh'ən) n.
arithmetic (ə-rĭth'mĭ-tĭk) Pronunciation Key
The mathematics of integers, rational numbers, real numbers, or complex numbers under the operations of addition, subtraction, multiplication, and division.
[n. uh-rith-muh-tik; adj. ar-ith-met-ik] 
(téchnē) (art, skill) of numbers, equiv. to arithmé(ein) to reckon + -t(o)- verbal adj. + -ik