Commelinids

The name commelinids is a plant taxonomy plural, not capitalised. It is used by the APG II system for a clade in the monocots, which in its turn is a clade in the angiosperms. 
The commelinids are the only clade that the APG II has named in the monocots. The remaining monocots are a paraphyletic unit, sometimes referred to as the "basal monocots".