adjective
(not comparable) Bearing full likeness by having precisely the same set of characteristics; indistinguishable.
(not comparable) Not different or other; not another or others; not different as regards self; selfsame; numerically identical.
(not comparable, biology) Of twins, sharing the same genetic code.
(not comparable, mathematics) Exactly equivalent.
(comparable, rare) Approximating or approaching exact equivalence.
noun
(usually pluralized, chiefly philosophy) Something which has exactly the same properties as something else.
An identical twin.
(poetry) A rhyme on the same syllable, such as "leave" and "believe".