The act or situation of relapsing. / (medicine) An occasion when a person becomes ill again after a period of improvement / (obsolete) One who has relapsed, or fallen back into error; a backslider.

(physics) The increased mass of an object moving at relativistic speed relative to an observer.

(physics) Of or relating to relativity. / (physics) At or near the speed of light. / (philosophy) Of or relating to relativism.

The act of being relegated / (sports) Moving from one division to a lower one, due to poor results

Experiencing or exhibiting relief; freed from stress or discomfort.

simple past tense and past participle of relieve

(set theory, order theory, "on" a set A) A subset of the Cartesian product A×A (the set of ordered pairs (a, b) of elements of A).

(set theory) A binary relation that is reflexive, symmetric and transitive.

(archaic) The surviving member of a married couple after one or the other has died; a widow or widower.

Surviving, remaining. / That is a relict; pertaining to a relict.