  This paper presents new results on the identities satisfied by the
hypoplactic monoid. We show how to embed the hypoplactic monoid of any rank
strictly greater than 2 (including infinite rank) into a direct product of
copies of the hypoplactic monoid of rank 2. This confirms that all hypoplactic
monoids of rank greater than or equal to 2 satisfy exactly the same identities.
We then give a complete characterization of those identities, and prove that
the variety generated by the hypoplactic monoid has finite axiomatic rank, by
giving a finite basis for it.

Rings and Algebras;Combinatorics;Group Theory