Infunctional analysis, a branch ofmathematics, abounding point of asubset of avector space is a conceptual extension of theboundary of aset.

Let${\displaystyle A}$  be a subset of a vector space${\displaystyle X}$ . Then${\displaystyle x\in X}$  is abounding point for${\displaystyle A}$  if it is neither aninternal point for${\displaystyle A}$  nor itscomplement.^[1]