An Etymological Dictionary of Astronomy and Astrophysics

Determining the three various parameters of a microlensing event
(the lens-source relative parallax and proper motion, and the mass of the lens)
from only one physical parameter (the event time scale). Currently
the microlensing degeneracy affects the vast majority of events and
makes any individual event impossible to interpret with certainty.

See also: → microlensing; → degeneracy.