n. A cutting in two; division into two parts or into twos; subdivision into halves or pairs; the state of being dichotomous.n. Specifically — In logic, the division of a whole into two parts; binary classification. Ramus revived, against the Aristotelians, the Platonic doctrine, which has had many adherents, that all classification should be by dichotomy. But the opinion has found little favor since Kant.n. In astronomy, that phase of the moon in which it appears bisected or shows only half its disk, as at the quadratures.n. In botany, a mode of branching by constant forking, as is shown in some stems, the venation of some leaves, etc. This mode of branching in plants is variously modified, as when only one of the branches at each fork becomes further developed, in which case the dichotomy is said to be sympodial. If these undeveloped branches lie always upon the same side of the axis, the sympodial dichotomy is helicoid; if alternately upon opposite sides, it is scorpioid.