Arithmet´ical, pertaining to arithmetic or its operations.—Arithmetical mean, the middle term of three quantities in arithmetical progression, or half the sum of any two proposed numbers; thus 11 is the arithmetical mean to 8 and 14.—Arithmetical progression, a series of numbers increasing or decreasing by a common difference, as 1, 3, 5, 7, &c.—Arithmetical signs, certain symbols used in arithmetic, and indicating processes or facts. The common signs used in arithmetic are the following:
A´rius, the originator of the Arian heresy. See Arians.