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

If you are taking a picture of the event with your smart phone you should protect your camera with a solar filter or you can just put a pair of eclipse glasses over the lens.

From BBC ● Aug. 10, 2026

Thirty minutes later, she was changing the car’s dirty air filter.

From The Wall Street Journal ● Aug. 1, 2026

Also rooted in old-school, so it spoke to my youth, but it’s through a psychedelic filter and musique concrète,” McFadden says.

From Los Angeles Times ● Jul. 29, 2026

In cities across the Midwest and Northeast, people wore masks outdoors to filter out the dangerous air.

From Barron's ● Jul. 17, 2026

Their mouths went dry from breathing in the ash-filled air, and they pulled their shirts up and over their heads to help filter out what particles they could.

From "Mountain of Fire" by Rebecca E. F. Barone

In addition, air purifiers — with carbon filters to control odor — would be in every classroom.

From Los Angeles Times ● Jul. 30, 2026

Citing the reduced risk, Anthropic said its automated safety filters will intervene roughly 85 percent less often on Opus 5 than on Fable 5, the Mythos-class model it released last month.

From Barron's ● Jul. 24, 2026

The experience showed her “there is demand for presenting yourself virtually and there’s a way to convey your cover-letter materials” that can get past new filters for job applications, which are fixated on certain keywords.

From MarketWatch ● Jul. 15, 2026

The site and app are entirely free, but two paid tiers offer more profile customization, filters and features, all with zero third-party ads.

From Salon ● Jul. 15, 2026

She had walked to another county once, hoping to trade some fabric she had sewn into filters for straining liquid in exchange for corn we could eat.

From "Lost Boy, Lost Girl" by John Bul Dau

That optimism filtered through to Asia, where Seoul -- which has been at the forefront of extreme volatility in the tech sector over the past month -- climbed more than four percent.

From Barron's ● Aug. 5, 2026

Together, these tools automatically filtered vast amounts of data before researchers performed additional analysis.

From Science Daily ● Jul. 14, 2026

Kyle Gordy does not drink alcohol or smoke, takes 30 supplements a day, eats only organic food and drinks nothing but filtered water.

From BBC ● Jul. 5, 2026

One thing we didn’t want to bring was a travel crib, so I filtered carefully for vacation rentals that had one.

From The Wall Street Journal ● Jun. 26, 2026

Sunlight filtered through the branches overhead, throwing spotlights on the path, and there was a certain distinctive, heady spring lightness in the air.

From "A Walk in the Woods" by Bill Bryson

Although the survey produced millions of potential detections, none survived all of the filtering steps.

From Science Daily ● Jul. 14, 2026

Like the living room, the bedroom is painted the same flat white but the quality of the eastern light filtering into the bedroom casts a buttery glow.

From Los Angeles Times ● Jun. 26, 2026

The theory behind it is how it separates teams on the result of the match between them, filtering out potentially big scorelines from other matches which can skew goal difference.

From BBC ● Jun. 23, 2026

Founded long before the generative AI boom created the risk of calls using "deepfake" voices resembling real friends or family, the company is now working on filtering potentially fraudulent conversations.

From Barron's ● Jun. 18, 2026

Finally, the setting sun, reddish orange, was filtering through the stable.

From "Rump: The (Fairly) True Story of Rumpelstilskin" by Liesl Shurtliff

Related Words

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