Quadrature may refer to:
Mathematics Quadrature (mathematics), a historic term for the computation of the area of a given plane figure, drawing a square with the same area, an integral or integration Squaring the circle Quadrature of the Parabola Quadrature of the hyperbola Numerical integration, calculating the numerical value of a definite integral, is often called "numerical quadrature" or simply "quadrature" Gaussian quadrature, a rule for numerical integration Quadrature (differential equations), expressing a differential equation solution in terms of antiderivatives
Signal processing Addition in quadrature, combining the magnitude of uncorrelated signals by taking the square root of the sum of their squares Quadrature phase, oscillations that are said to be in quadrature if they are separated in phase by 90° (/2, or /4) Quadrature component of a composite signal Quadrature filter, the analytic signal of a real-valued filter Quadrature amplitude modulation (QAM), a modulation method of using both an (in-phase) carrier wave and a 'quadrature' carrier wave that is 90° out of phase with the main, or in-phase, carrier Quadrature phase-shift keying (QPSK), a phase-shift keying of using four quadrate points on the constellation diagram, equispaced around a circle
Science Optical phase space quadratures, operators which represent the real and imaginary parts of the complex amplitude Quadrature (astronomy), the position of a body (moon or planet) such that its elongation is 90° or 270°; i.e., the body-earth-sun angle is 90°
Other uses Quadrature encoder, a device that detects mechanical position changes and direction of movement Illusionistic ceiling painting, sometimes called quadrature after the Italian term, quadratura La Quadrature du Net (Squaring of the Net in French), a French advocacy group that promotes digital rights and freedoms of citizens "Quadrature", a song by Squarepusher from the album Just a Souvenir