Dichotomy
Etymology
From Greek dichotomia, “a cutting in two,” from dicha, “in two, apart,” + temnein, “to cut.” The literal “cut in two” is exactly the modern sense: a clean division into two contrasting categories.
noun · /dye-KOT-uh-mee/
A division of something into two sharply opposed or mutually exclusive parts.
What it names
The specific shape of an either/or split, and flags when two things are being treated as exhaustive opposites — often exposing a false choice.
Example
The debate assumed a dichotomy between safety and freedom, as if you could never have more of both.
Related idea
A dichotomy insists on two discrete camps; a spectrum spreads the same territory across a continuous range of degrees.