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Filter, filtering or filters may refer to:

Chemistry, engineering and materials[edit]

  • Filter (aquarium), critical components of both freshwater and marine aquaria
  • Filter (chemistry), a device (usually a membrane or layer) that is designed to physically block certain objects or substances while letting others through
  • Filter paper, a semi-permeable paper barrier placed perpendicular to a liquid or air flow. It is used to separate fine solids from liquids or air
  • Air filter, a device composed of fibrous materials which removes solid particulates such as dust, pollen, mold, and bacteria from the air
  • Oil filter, a filter to remove contaminants from engine oil, transmission oil, lubricating oil, or hydraulic oil
  • Pneumatic filter, a device which removes contaminants from a compressed air stream
  • Water filter, removes impurities from water by means of a fine physical barrier, a chemical process or a biological process. Filters cleanse water to various extents for irrigation, drinking water, aquariums, and pools
  • Sieve or macroscopic filter

Optics and photography[edit]

In optics and photography, a device to remove, or to enhance, certain ranges of wavelengths (colors) of light. See:

Turbulence modeling[edit]

In turbulence modeling, a procedure to dampen or remove the highest frequencies of the flow:

  • Filter (large eddy simulation), in the context of large eddy simulation (LES) is a mathematical operation intended to remove a range of small scales from the solution to the Navier-Stokes equations

Signal processing[edit]

In signal processing, especially electronics, an algorithm or device for removing part(s) of a signal:


In computing:

  • Filter (higher-order function), a higher-order function that processes a data structure (typically a list) in some order to produce a new data structure containing exactly those elements of the original data structure for which a given predicate returns the boolean value true
  • A program to process a data stream:
    • Filter (software), a computer program to process a data stream
    • Filter (Unix), a program that gets most of its data from its standard input (the main input stream) and writes its main results to its standard output (the main output stream)
    • Filter (video)
    • Email filter
    • Internet filter
    • Wordfilter, a script typically used on Internet forums or chat rooms that automatically scans users' posts or comments as they are submitted and automatically changes or censors particular words or phrases
  • BPF filter expression used in the qualification of network data
  • DSL filter, a low-pass filter installed between analog devices and a telephone line



  • In mathematics. See:
  • In psychology, a type of learning blockage. See:
    • Affective filter, an impediment to learning or acquisition caused by negative emotional ("affective") responses to one's environment. It is a hypothesis of second language acquisition theory, and a field of interest in educational psychology
  • In transportation. See:
    • Lane splitting, a practice that cyclists use to pass slow or stopped congested traffic

Proper name[edit]

See also[edit]