Filter is a device or process that removes unwanted components from a substance or signal.
In technology, filter refers to:
1. A software function that processes data (e.g., email filters)
2. A hardware component that blocks certain frequencies (e.g., audio filters)
3. In photography, optical filters that modify light entering the lens
In everyday life, filter can mean:
1. Water filters that purify drinking water
2. Air filters that remove pollutants
3. Cigarette filters that reduce harmful substances