nullity

/N AH1 L AH0 T IY0/
noun
  1. 1

    The state of being null, or void, or invalid.

    โ€œnullity of marriageโ€

  2. 2

    A void act; a defective proceeding or one expressly declared by statute to be a nullity.

  3. 3

    The difference between the rank of a matrix and the number of columns it has; the dimension of the nullspace of a matrix.

Source: https://en.wiktionary.org/wiki/nullity