Generally, a trichotomy is a splitting into three disjoint parts. In mathematics, the most concrete law of trichotomy that is usually seen is the statement that for any real numbers x and y, exactly one of the following relations holds:
x < y,
x = y,
x > y.
More generally, a law of trichotomy is any statement that for some binary relation on some set S, which we may denote by using the "less than" symbol "<", and for any two members x, y ∈ S, exactly one of the relations above holds. For a transitive binary relation this is exactly equivalent to saying that the binary relation in question is a linear ordering of the set S.
In taxonomy a trichotomy is speciation of three groups from a common ancestor, where it is unclear or unknown in what chronological order the three groups split.
The trichotomous model and investment in learning to prepare for a sport test: A mediational analysis
The study was designed to investigate the direct and mediational effects of three experimental goal conditions on the time in which pupils prepared for a sport test.
The trichotomous model appears to be valid for the study of motivational processes in school physical education.