Duplicate

Double; twofold.

That which exactly resembles or corresponds to something else; another, correspondent to the first; hence, a copy; a transcript; a counterpart.

An original instrument repeated; a document which is the same as another in all essential particulars, and differing from a mere copy in having all the validity of an original.

To double; to fold; to render double.

To make a duplicate of (something); to make a copy or transcript of.

To divide into two by natural growth or spontaneous action; as, infusoria duplicate themselves.

something additional of the same kind; "he always carried extras in case of an emergency"