Latin. From the beginning; from the first act
A party is said to be a trespasser ab initio, an estate to be good ab initio, an agreement or deed to be void ab initio, a marriage to be unlawful ab initio, and the like. Plow. 6a, 16a; 1 BI. Comm. 440
A agreement without consideration is an unenforceable contract ab initio.