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.

(informal, idiomatic) To be very frightened, scared, or nervous.

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

(nanotechnology) A fluorescent nanoparticle of semiconducting material.

a quantum well incorporated in a quantum dot

(quantum mechanics) a potential well that confines particles in one dimension, forcing them to occupy a planar region

having four parts / four times over, multiplied by four