Nullity
Nullity is a term used in several disciplines to indicate an absence or zero dimension of a specified object. In mathematics, especially linear algebra, nullity of a linear transformation or matrix is the dimension of its kernel—the set of all vectors that map to the zero vector. For a matrix A with n columns, the nullity is the dimension of the solution space to Ax = 0. The nullity is connected to the rank by the rank-nullity theorem: rank(A) + nullity(A) = n. This means nullity measures how many independent solutions exist to the homogeneous system Ax = 0. For example, a full-rank square matrix has nullity 0, while a matrix with more columns than its rank has positive nullity.
In law, nullity of marriage refers to a declaration that a marriage is invalid from the outset.
Other uses of the term are less common but may appear in philosophy or logic to denote