Other forms: filters, filtering, filtered
A filter is anything that lets some things through and holds the rest back. The paper cone that keeps the coffee grounds out of your cup, the mesh in a vacuum cleaner, the round glass a photographer screws onto a lens to change the light.
As a verb it runs both ways: you filter water, and light filters through the curtains. Filter out is the everyday phrasal verb — a spam filter filters out junk before you see it. The word has spread to anything that sorts and blocks: a search filter, a parental filter, the colour filter on a photo app, and 'no filter' for someone who says whatever comes into their head. British drivers meet a filter lane and a green filter arrow, where traffic peels off to turn.
1nounstrainerA device or material that liquid, air or light passes through so unwanted parts are held back.
“He changed the filter on the fish tank at the weekend.”
2nounfilterA piece of coloured or treated glass fitted over a lens to change the light reaching it.
“A polarising filter cut the glare off the water.”
3verbpassTo pass something through a filter to clean it or separate parts of it.
“The machine filters the water twice before it reaches the tap.”
4verbmoveTo move through slowly, in small amounts or a few at a time.
“News of the result filtered through the office by lunchtime.”
5nounsettingA setting that shows only the items you choose, or blocks unwanted ones.
“Add a filter so you only see unread messages.”
FILTER → the one you put on a picture before posting
The one you put on a picture before you post it, and the glass one on a camera does the same job: it sits in front and changes the light that gets through.
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Filter came through Middle English filtre from Medieval Latin filtrum, which Latin had taken from Frankish *filtir and Proto-West Germanic *felt — the same word as felt, the matted wool cloth, from a root *pel- meaning 'beat'. Felt is made by beating wool into a mat, and before paper cones that mat is what you strained your liquid through. The cloth handed its name to the job.
Proto-Indo-European
*pel- (beat)
Proto-West Germanic
*felt
Frankish
*filtir
Medieval Latin
filtrum
Middle English
filtre
English, today
filter
From Middle English filtre, from Medieval Latin filtrum (compare also Old French feutre (“felt; filter”)), from Frankish filtir, from Proto-West Germanic felt. See felt. a doublet of phin.
Etymology from Wiktionary, CC BY-SA