Quadrature may refer to:
In signal processing:
- 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, oscillations that are said to be in quadrature if they are separated in phase by 90° (π/2, or λ/4)
- Quadrature filter, the analytic signal of a real-valued filter
- Quadrature phase-shift keying (QPSK), a phase-shift keying of using four quadrate points on the constellation diagram, equispaced around a circle
In mathematics:
- Quadrature (mathematics), drawing a square with the same area as a given plane figure (squaring) or computing that area
- Numerical integration is often called 'numerical quadrature' or simply 'quadrature'
- Gaussian quadrature, a special case of numerical integration
In physics:
- In Optical phase space, quadratures are operators which represent the real and imaginary parts of the complex amplitude
In astronomy:
- Quadrature (astronomy), the position of a body (moon or planet) such that its elongation is 90° or 270°; i.e. the sun-earth-body angle is 90°
Quadrature may also refer to:
- In motion control, quadrature encoder is a rotary encoder or linear encoder giving both the relative position and the direction of motion of a shaft