The Gbe languages form a cluster of about 20 related languages stretching across the area between eastern Ghana and western Nigeria. The total number of speakers of Gbe languages is between four and eight million. The most widely spoken Gbe language is Ewe, followed by Fon. The Gbe languages belong to the Kwa branch of the Niger–Congo languages, and break up into five major dialect clusters: Ewe, Fon, Aja, Gen, and Phla–Pherá. In the late 18th century, many speakers of Gbe were enslaved and transported to the New World, causing Gbe languages to play a role in the genesis of several Caribbean creole languages. In the first half of the twentieth century, the Africanist Diedrich Hermann Westermann was one of the most prolific contributors to the study of Gbe. The first internal classification of the Gbe languages was published in 1988 by H.B. Capo, followed by a comparative phonology in 1991. The Gbe languages are tonal, isolating languages and the basic word order is subject–verb–object.