Filter (noun)

1. A device for suppressing or reducing the amplitude of unwanted frequencies or signals.
2. A porous material or device through which a liquid or gas is passed to remove suspended impurities or to recover a soluble substance.

Origin:

Late 16th century: from french filtre or latin filtrum, from filum "thread".

Examples:

1. The water filter removes impurities from the water.
2. He installed a filter on his camera lens.
3. The filter in the air conditioning system needed to be cleaned.
4. The filter on the microphone helps to reduce background noise.
5. She used a filter in her photo editing software to enhance the colors.