These are the unifoliate, which have one leaf, and the bifoliate, which have two.    From Wordnik.com.  [Article Source] Reference

I see that I have probably gone beyond my depth in discussing plurifoliate and unifoliate leaves; but in such a case as that of Mimosa albida, where rudiments of additional leaflets are present, we must believe that they were well developed in the progenitor of the plant.    From Wordnik.com.  [More Letters of Charles Darwin — Volume 2] Reference