Divided into four parts. / Involving four parties or participants; four-party.

A treatise divided into four parts.

(finance) Simultaneous expiry on US markets of stock index futures, stock index options, stock options, and single stock futures, which takes place on the third Friday of March, June, September, and December. (Prior to single stock futures those days were triple witching.)

(number theory) The mathematical theorem which states that, for given odd prime numbers p and q, the question of whether p is a square modulo q is equivalent to the question of whether q is a square modulo p.

(mathematics) A number (real or complex) which is a solution to an equation of the form x²+Bx+C=0 for some integers B and C. For example 42, or 2+3i, or 1+√/2.

Having the shape of a quadrangle; in the shape of a quadrangle.

having four parts / four times over, multiplied by four

in quadruplicate: four times over, in four copies

To replicate four times; to make fourfold; to quadruple.

Happening every four years. / Lasting for four years.