Filter

• Filter (higher-order function), in functional programming
• Filter (software), a computer program to process a data stream
• Filter (video), a software component that performs some operation on a multimedia stream
• Information filtering system
• Email filtering, the processing of email to organize it according to specified criteria
• Content-control software also known as an Internet filter
• Wordfilter, a script typically used on Internet forums or chat rooms
• Berkeley Packet Filter, filter expression used in the qualification of network data
• DSL filter, a low-pass filter installed between analog devices and a telephone line
• Helicon Filter, a raster graphics editor
• Filter (large eddy simulation), a mathematical operation intended to remove a range of small scales from the solution to the Navier-Stokes equations
• Kalman filter, an approximating algorithm in optimal control applications and problems
• Filter (social media), an appearance-altering digital image effect for social media

• Filter (chemistry), a device which separates solids from fluids (liquids or gases) by adding a medium through which only the fluid can pass
• Filter (aquarium), critical components of both freshwater and marine aquaria
• 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
• Cigarette filter, a part of a cigarette intended to filter the smoke inhaled by a smoker
• Coffee filter, a utensil used to separate coffee grounds from liquid coffee
• Fuel filter, found in most internal combustion engines
• Filtration (wine)
• Sieve or macroscopic filter, a device for separating wanted elements from unwanted material

• Filter (mathematics), a special subset of a partially ordered set.
• Filter (set theory), a special family of subsets that forms an (order theoretic) filter with respect to set inclusion
• Filters in topology, the use of collections of subsets to describe convergence.
• Filtering problem (stochastic processes), a mathematical model for a number of filtering problems in signal processing and the like.
• Filtration (mathematics), an indexed set of subobjects of a given algebraic structure S.

• Optical filter, selectively transmits light of different wavelengths
• Interference filter, reflects one or more spectral bands or lines and transmits others, while maintaining a nearly zero coefficient of absorption for all wavelengths of interest
• Dichroic filter, a very accurate color filter used to selectively pass light of a small range of colors while reflecting other colors
• Hydrogen-alpha filter, an optical filter that transmits a narrow bandwidth of light centred on the H-alpha wavelength
• Photographic filter, a camera accessory consisting of an optical filter that can be inserted in the optical path
• Infrared cut-off filter, designed to reflect or block mid-infrared wavelengths while passing visible light
• Chelsea filter, a dichromatic optical filter used for identifying coloured stones
• Astronomical filter, a telescope accessory used to enhance the details of celestial objects

• Filter (signal processing)
• Electronic filter, an electronic circuit which processes signals, for example to remove unwanted frequency components
• Digital filter, a system that performs mathematical operations to reduce or enhance certain aspects of a signal
• Analogue filter, a basic building block of signal processing much used in electronics
• Filters used in digital image processing

• Filter (TV series), a show on the G4 channel
• Filter (magazine), an indie music magazine
• Filter Theatre, a British theatre company
• The Filter, a digital content services company based in England
• Filter (band), an American rock band
• "Filter", a song from the album Bend by 8stops7
• "Filter", a song from the album Map of the Soul: 7 by BTS
• "Filter", a song from the album Ruby by Jennie

• Biofilter, a pollution control technique using a bioreactor containing living material to capture and biologically degrade pollutants
• Filtering (housing), the process of housing units becoming more affordable with age
• Category-based filtering of perception, according to (objectivist interpretations of) Kant
• Affective filter, an impediment to learning or acquisition caused by negative emotional ("affective") responses to one's environment
• Lane splitting, a practice that cyclists use to pass slow or stopped congested traffic
• The ability of a person to self-censor themselves (their thoughts) whilst speaking

• Filter coffee, a method for preparing coffee
• Filter feeder, an animal that strains food particles from water
• Filtration camp (disambiguation)
• Lifter (signal processing)
• Philtre (disambiguation)
• Separation process
• Ultrafilter

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