Hornbeams are relatively small hardwood trees in the genus Carpinus. Though some botanists grouped them with the hazels (Corylus) and hop-hornbeams (Ostrya) in a segregated family, Corylaceae, modern botanists place the hornbeams in the birch subfamily Coryloideae. The 30–40 species occur across much of the north temperate regions, with the greatest number of species in east Asia, particularly China. Only two species occur in Europe, only one in eastern North America, and one in Mesoamerica. Carpinus betulus can be found in Europe, Turkey and Ukraine.