a (not comparable) Bearing full likeness by having precisely the same set of characteristics; indistinguishable.
a (not comparable) Not different or other; not another or others; not different as regards self; selfsame; numerically identical.
a (not comparable) Having some particular qualities or characteristics in common, but not all of them.
n (usually|pluralized|chiefly|philosophy) Something which has exactly the same property | properties as something else.