Filter

Filter may refer to:

Chemistry, engineering and materials

In chemistry, engineering, or household usage, a device to separate mixtures. See:
* Filter (chemistry)
* Water filter
* Air filter
* Oil filter
* Pneumatic filter

Optics and photography

In optics and photography, a device to remove, or to enhance, certain ranges of wavelengths (colors) of light. See:
*filter (optics)
*photographic filter
*infrared filter
*H-alpha filter
*Chelsea filter

Signal processing

In signal-processing applications (such as telecommunications, music, and picture processing): a mathematical algorithm, or an electrical or mechanical device, to modify the contents of signals and to extract their salient features. See:

* electronic filter
* audio filter
* line filter
* digital filter
* Wiener filter
* Kalman filter

See filtering problem (stochastic processes) for the mathematical formalism.

Computing

In computing:
* filter (higher-order function)
* A program to process a data stream:
** filter (software)
**filter (Unix)
** mail filter
** Internet filter
** wordfilter
** DirectShow
* BPF filter expression used in the qualification of network data

Philosophy

* Category-based filtering of perception — according to (objectivist interpretations of) Kant
* interpretive filtering through concepts according to existentialism

Other

* In mathematics, a certain kind of subset of a partially ordered set. See
** filter (mathematics).
* In psychology, a type of learning blockage. See
** affective filter.
* In transportation, filtering forward, a practice that cyclists use to pass slow or stopped congested traffic.
* An aquarium filter.

Proper name

* Filter (band), an industrial rock band
* "Filter (television)", a show on the G4 channel:
* "Filter (magazine)", an off-beat indie music magazine
* Helicon Filter, a raster graphics editor

See also

* Filter coffee, a method for preparing coffee
* Filter feeder, an animal that strains food particles from water
* Philter, a magical potion
* Filtration
* Conversion