adj

• (not comparable) Bearing full likeness by having precisely the same set of characteristics; indistinguishable.
  "My car is identical with the one my mom has just bought."
• (not comparable) Not different or other; not another or others; not different as regards self; selfsame; numerically identical.
  "The best of the joke, too, is, that the very coal-merchant who is loudest in his complaints against the person who defrauded him, is the identical man who sat in the centre of the very front row of the pit last night and laughed the most boisterously at this very same thing,--and not so well done either."
• (not comparable, biology) Of twins, sharing the same genetic code.
• (not comparable, mathematics) Exactly equivalent.

noun

• (usually pluralized, chiefly philosophy) Something which has exactly the same properties as something else.
• (poetry) A rhyme on the same syllable, such as "leave" and "believe".
  "The strictest construction of the rule requires complete and unvarying repetition of end-words, but some license is granted in the use of identicals."