Filter

[fil-ter] /ˈfɪl tər/

noun
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.
Informal. a filter-tipped cigarette or cigar.
5.
Photography. a lens screen of dyed gelatin or glass for controlling the rendering of color or for diminishing the intensity of light.
6.
Electronics, Physics. a circuit or device that passes certain frequencies and blocks others.
7.
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.
verb (used with object)
8.
to remove by the action of a filter.
9.
to act as a filter for; to slow or partially obstruct the passage of:
The thick leaves filtered the sunlight.
10.
to pass through or as through a filter.
verb (used without object)
11.
to pass or slip through slowly, as through an obstruction or a filter:
Enemy agents managed to filter into the embattled country.
/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.
(Brit) 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
verb
7.
(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
8.
(transitive) to obtain by filtering
9.
(intransitive) foll by through. to pass (through a filter or something like a filter): dust filtered through the screen
10.
(intransitive) to flow slowly; trickle
n.

early 15c., from Old French filtre and directly from Medieval Latin filtrum “felt,” which was used to strain impurities from liquid, from West Germanic *filtiz (see felt (n.)). Of cigarettes, from 1908.
v.

1570s, from Medieval Latin filtrare, from filtrum (see filter (n.)). The figurative sense is from 1830. Related: Filtered; filtering.

filter fil·ter (fĭl’tər)
n.

v. fil·tered, fil·ter·ing, fil·ters

fil’ter·er n.
fil’ter·less adj.
filter
(fĭl’tər)

A computer software program that selectively screens out incoming information.

Note: 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.

1. (Originally Unix, now also MS-DOS) A program that processes an input data stream into an output data stream in some well-defined way, and does no I/O to anywhere else except possibly on error conditions; one designed to be used as a stage in a pipeline (see plumbing). Compare sponge.
2. (functional programming) A higher-order function which takes a predicate and a list and returns those elements of the list for which the predicate is true. In Haskell:
filter p [] = [] filter p (x:xs) = if p x then x : rest else rest where rest = filter p xs
See also filter promotion.
[Jargon File]