The **kernel** in geometry is the set of all points *a* such that for all points *b* inside a polygon *P*, the segment *ab* lies entirely within *P*.^{[1]}

In abstract algebra, the **kernel** of a function between two groups is the set of all members of the first which map to the identity of the second. Similarly, the **kernel** of a mapping in linear algebra from one vector space to another is the set of vectors mapped to the zero vector.