What is Principal Fact?

Legal Definition
In the law' of evidence. A fact sought and proposed to be proved by evidence of other facts (termed "evidentiary facts") from which it is to be deduced by inference. A fact which is the principal and ultimate object of an inquiry, and respecting the existence of which a definite belief is required to be formed. 3 Benth. Jud. Ev. 3; Burrill, Circ. Ev. 3, 119
-- Black's Law Dictionary
Legal Definition
the term that is used for the main fact that is in dispute in a case.
Legal Definition
The main fact at issue in a cause.
-- Ballentine's Law Dictionary