Null: undefined, empty, or meaningless value.

Examples in Micing techniques to reduce bleed or unwanted standing Waves: Always aI'm the null of the polar pattern at the offending noise source. For example, if recording a snare drum aI'm the null of the mic at the high-hat to reduce high-hat leakage into the snare mic.

In mathematics, the word null (from German null, which is from Latin nullus, both meaning "zero", or "none") means of or related to having zero members in a set or a value of zero. Sometimes the symbol ∅ is used to distinguish "null" from 0.

In radio electronics, a null is an area or vector in an antenna's radiation pattern where the signal cancels out almost entirely.