filter

American  

[fil-ter] / ˈfɪl tər /

noun

• filters
  plural

1. any substance, as cloth, paper, porous porcelain, or a layer of charcoal or sand, through which liquid or gas is passed to remove suspended impurities or to recover solids.

2. any device, as a tank or tube, containing such a substance for filtering.

3. any of various analogous devices, as for removing dust from air or impurities from tobacco smoke, or for eliminating certain kinds of light rays.

4. something that works like a filter, as by removing, blocking, or separating out certain elements.

   Kids often talk without a filter. Events can be distorted through the filter of memory.

5. Informal. a filter-tipped cigarette or cigar.

6. Photography.

   1. a lens screen of dyed gelatin or glass placed on a camera for controlling the rendering of color or for diminishing the intensity of light.

   2. Digital Technology. a data manipulation function that changes the color or sharpness of a digital image or overlays an additive or special effect element.

      Use a sepia filter to give your photos that old-timey look.

7. Electronics, Physics. a circuit or device that passes certain frequencies and blocks others.

8. Mathematics. a collection of subsets of a topological space, having the properties that the intersection of two subsets in the collection is a subset in the collection and that any set containing a subset in the collection is in the collection.

9. Computers. an algorithm that categorizes, sorts, prioritizes, or blocks data through rule-based protocols.

   an email filter that deletes messages with subject words found commonly in spam.

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verb (used with object)

• filters,
  present (3rd person singular)
• filtered,
  past participle,  past
• filtering
  present participle

1. to remove by the action of a filter.

2. Computers. to subject (data) to an algorithmic filter.

   The search engine will filter your query results based on your location and user profile.

3. to act as a filter for; to slow or partially obstruct the passage of.

   The thick leaves filtered the sunlight.

4. to pass through or as through a filter.

verb (used without object)

• filters,
  present (3rd person singular)
• filtered,
  past participle,  past
• filtering
  present participle

1. to pass or slip through slowly, as through an obstruction or a filter.

   Enemy agents managed to filter into the embattled country.

   Synonyms:

   leak, trickle, seep, sift, penetrate

filter British  

/ ˈfɪltə /

noun

1. a porous substance, such as paper or sand, that allows fluid to pass but retains suspended solid particles: used to clean fluids or collect solid particles

2. any device containing such a porous substance for separating suspensions from fluids

3. any of various porous substances built into the mouth end of a cigarette or cigar for absorbing impurities such as tar

4. any electronic, optical, or acoustic device that blocks signals or radiations of certain frequencies while allowing others to pass See also band-pass filter

5. any transparent disc of gelatine or glass used to eliminate or reduce the intensity of given frequencies from the light leaving a lamp, entering a camera, etc

6. a traffic signal at a road junction consisting of a green arrow which when illuminated permits vehicles to turn either left or right when the main signals are red

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verb

1. (often foll by out) to remove or separate (suspended particles, wavelengths of radiation, etc) from (a liquid, gas, radiation, etc) by the action of a filter

2. (tr) to obtain by filtering

3. to pass (through a filter or something like a filter)

   dust filtered through the screen

4. (intr) to flow slowly; trickle

filter Scientific  

/ fĭl′tər /

1. A material that has very tiny holes and is used to separate out solid particles contained in a liquid or gas that is passed through it.

2. A device that allows signals with certain properties, such as signals lying in a certain frequency range, to pass while blocking the passage of others. For example, filters on photographic lenses allow only certain frequencies of light to enter the camera, while polarizing filters allow only light polarized along a given plane to pass. Radio tuners are filters that allow frequencies of only a narrow range to pass into an amplification circuit.

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filter Cultural  

1. A computer software program that selectively screens out incoming information.

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Discover More

Spam may be the target of a filter, or parents may use a filter designed to prevent their child's access to pornographic or violent Web pages.

Other Word Forms

Derived Forms

• filterer
  noun
• nonfilter
  noun
• prefilter
  noun
• overfilter
  verb (used with object)
• refilter
  verb (used with object)
• unfiltering
  adjective
• well-filtered
  adjective

Inflected Forms

Nouns

• filters
  plural

Participles

• filtering
  present
• filtered
  past

Conjugated Forms

Present

• filter
  simple
• filters
  simple
• have filtered
  perfect
• has filtered
  perfect
• am filtering
  progressive
• are filtering
  progressive
• is filtering
  progressive
• have been filtering
  perfect progressive
• has been filtering
  perfect progressive

Past

• filtered
  simple
• had filtered
  perfect
• was filtering
  progressive
• were filtering
  progressive
• had been filtering
  perfect progressive

Future

• will filter
  simple
• will have filtered
  perfect
• will be filtering
  progressive
• will have been filtering
  perfect progressive

Etymology

Origin of filter

First recorded in 1375–1425; late Middle English filtre, from Medieval Latin filtrum “felt, piece of felt used to strain liquids,” from Germanic; see origin at felt ²

Explanation

A machine or device that removes dangerous or unwanted materials from a substance passing through it is called a filter. A kitchen water filter makes the water safer to drink — and also taste better. Cars have many different filters, each of which takes impurities out of air, fuel, or water before it enters the car's engine. Most coffee makers require paper filters that allow brewed coffee to flow into the pot while leaving the coffee grounds behind. Filter is also a verb, meaning to strain or remove particular particles. The Medieval Latin root is filtrum, or "felt," which was used by early chemists to strain liquids, especially when purifying water.

Example Sentences

See Examples For:

filter filters filtered filtering

For example, the agents circumvented a filter on the website that was blocking their requests for data, she said, ultimately using a technique that the website operators didn’t permit.

From The Wall Street Journal ● Sep. 27, 2026

Meta has denied the allegations in the lawsuit and says it has taken “steps to filter this data to help remove identifying information and to protect people’s privacy.”

From Los Angeles Times ● Sep. 24, 2026

The NHS advises pregnant women, external to keep caffeine intake below 200mg a day, about two mugs of filter coffee, as studies have linked it to low birth weight and other complications.

From BBC ● Sep. 17, 2026

Higher prices for a barrel of oil take time to filter down to retail gas prices, but a look at the oil market’s “prompt spread” shows bigger gas bills look likely.

From MarketWatch ● Sep. 14, 2026

Since then, I've used 131 hours of filter on various EVAs.

From "The Martian" by Andy Weir

It will also strengthen age verification, ban beauty filters for teenagers, and offer young users a non-personalized content feed.

From Barron's ● Sep. 26, 2026

Children’s products, water filters and power tools also compete on safety.

From The Wall Street Journal ● Sep. 16, 2026

Roman's Coronagraphic Instrument will use masks, prisms, detectors, filters, and self-flexing mirrors to demonstrate technologies capable of suppressing starlight.

From Science Daily ● Aug. 28, 2026

Teens wouldn’t be able to use extreme makeup filters.

From Los Angeles Times ● Aug. 28, 2026

Toby waited as Lily looked for coffee, then filters.

From "We'll Fly Away" by Bryan Bliss

Text-based learning, even when filtered through a trillion-strong “weightings” map, is only partial knowledge of the world.

From The Wall Street Journal ● Sep. 25, 2026

From there, medbeds filtered out to the rest of the secret-space-program community and to other alternative subcultures, including the New Age world.

From Slate ● Sep. 22, 2026

Chris Lofts, the site manager, said the waste was first filtered before having water added and being fed into a digester to create methane.

From BBC ● Aug. 27, 2026

Flores, whose only public comments had for months been filtered through his legal team, agreed to speak with The Times, detailing the toll that the prior year and a half had taken on him.

From Los Angeles Times ● Aug. 26, 2026

The telltale smell of smoke filtered in through the open windows.

From "The Darkest Minds" by Alexandra Bracken

I realized I was nervous and not filtering my words very well.

From Los Angeles Times ● Sep. 18, 2026

It holds huge amounts of water, slowing rain as it moves downhill, reducing flooding and filtering out sediment before it reaches the reservoir.

From BBC ● Sep. 12, 2026

Yet when it comes to the ways AI is filtering into Americans’ jobs, many workers are looking at a trickle so far, rather than a flood.

From MarketWatch ● Sep. 1, 2026

Scientists have long thought that worker bees help shield queens from contamination by filtering harmful substances out of the food they provide.

From Science Daily ● Aug. 22, 2026

This filtering phenomenon is very widespread and manifests itself in many ways.

From "Innumeracy: Mathematical Illiteracy and Its Consequences" by John Allen Paulos

Related Words

• clean
• drain
• dribble
• leak
• penetrate
• percolate
• permeate
• refine
• sift
• trickle
• winnow