Arithmetik
Arithmetic or arithmetics (from the Greek word ἀριθμός, arithmos "number") is the oldest and most elementary branch of mathematics, used by almost everyone, for tasks ranging from simple day-to-day counting to advanced science and business calculations. It involves the study of quantity, especially as the result of operations that combine numbers. In common usage, it refers to the simpler properties when using the traditional operations of addition, subtraction, multiplication and division with smaller values of numbers. Professional mathematicians sometimes use the term (higher) arithmetic when referring to more advanced results related to number theory, but this should not be confused with elementary arithmetic.
Read more about Arithmetik: History, Arithmetic Operations, Decimal Arithmetic, Compound Unit Arithmetic, Number Theory, Arithmetic in Education