filter

1. A device which separates a suspended, dissolved, or particulate matter from a fluid, solution, or other substance; any device that separates one substance from another.
2. Electronics or software that separates unwanted signals (for example noise) from wanted signals or that attenuates selected frequencies.
3. Any item, mechanism, device, or procedure that acts to separate or isolate. · He runs an email filter to catch the junk mail.
4. Self-restraint in speech. (figuratively) · He's got no filter, and he's always offending people as a result.
5. A non-empty upper set (of a partially ordered set) which is closed under binary infima (a.k.a. meets).
6. A translucent object placed in the light path of a camera to remove certain wavelengths (colors), or a computer program that simulates such an effect.
7. An appearance-altering digital image effect.

Plural filters