dichotomie

Dichotomie, closely related to the English term dichotomy, is a concept describing a division of a whole into two parts that are mutually exclusive and collectively exhaustive. In a dichotomy, every element belongs to one of the two parts, and the parts do not overlap. The word comes from Greek di- “two” and temnein “to cut.”

Applications unfold across disciplines. In philosophy and logic, dichotomies frame opposing positions or fundamental distinctions, such as mind vs. body or nature vs. culture. In mathematics and statistics, a dichotomous or binary variable takes one of two values, such as yes/no or true/false. In biology, a dichotomous key guides identification by a sequence of paired choices, with each step splitting an option into two alternatives. In the social sciences, binary classifications are common but criticized for oversimplifying complex continua.

Limitations and alternatives are routinely discussed. Many phenomena are not strictly binary; they exhibit gradations or multiple categories. Relying on dichotomies can obscure nuance, context, or probability. Alternative approaches include polytomous classifications, probabilistic models, or multi-valued logics that allow more than two categories or degrees of belief. The concept is also related to binary opposition in semiotics and to decision trees in data analysis.