The dependence of a system's current state on its history — in physics, a lag between cause and effect, as with magnetic lag; in economics, unemployment that persists after a recession longer than the business cycle alone would predict.
Hysteresis is the dependence of a system’s present state on its history, such that the path back differs from the path out and the system does not simply return when a cause is withdrawn. The term comes from physics and materials science, where magnetisation and stress–strain behaviour show characteristic loops, and it has been carried into economics. There the word names a substantive and contested empirical claim rather than a definition: that a temporary shock — a recession, a spell of unemployment — can permanently shift the long-run level of a variable rather than leaving it to recover. Whether that holds, and by what mechanism, is disputed. The economic usage borrows the physical term’s suggestiveness rather than its measurable form.
Why this entry carries no source list. This lexicon cites an official primary source wherever one exists. For a concept used across several traditions at once, no such source exists: there is no body with authority over it, and a signed academic reference — the tier this lexicon would otherwise reach for — has no entry under this headword. Citing one school’s formulation would present a position as a definition. So the entry names the senses in play and the distinction between them, which is the part a reader can actually use.