In plant taxonomy, commelinids (originally commelinoids) (plural, not capitalised) is a name used by the APG IV system for a clade within the monocots, which in its turn is a clade within the angiosperms. The commelinids are the only clade that the APG has informally named within the monocots. The remaining monocots are a paraphyletic unit. Also known as the commelinid monocots it forms one of three groupings within the monocots, and the final branch, the other two groups being the alismatid monocots and the lilioid monocots. 

Members of the commelinid clade have cell walls containing UV-fluorescent ferulic acid. 

The commelinids were first recognized as a formal group in 1967 by Armen Takhtajan, who named them the Commelinidae and assigned them to a subclass of the monocots. However, by the release of his 1980 system of classification, he had merged this subclass into a larger one no longer considered to be a clade. 

The commelinids constitute a well-supported clade within the monocots, and this clade has been recognized in all four APG classification systems. 

The commelinids of APG II (2003) and APG III (2009) contain essentially the same plants as the commelinoids of the earlier APG system (1998). In APG IV (2016) the family Dasypogonaceae is no longer directly placed under commelinids but instead a family of order Arecales.
under what is it?
order Arecales.