The language has between 20 to 30 dialects. The major division is between the Onicha group in the north and the Owere group in the south. Since the 19th century there has been several attempts to develop a written standard language, starting with Isuama Igbo (1857-1905) and continuing with Union Igbo (1905-41), Central Igbo (1941-73), and Standard Igbo (1973 to present).
•Isuama Igbo was spoken by freed Igbo slaves in Sierra Leone, as a sort of lingua franca between different Igbo communities, but was quite removed from any Igbo dialect of the Igbo homeland.
•Union Igbo was an answer to the growing number of Christian Igbos within Nigeria but being rather artificial it was employed only as a liturgical and literary language.
•Central Igbo, based on the Owerri and Umuahia dialects, was the vehicle of many translations from European Literature.
•Standard Igbo, implemented after the independence of Nigeria, is also based on the Owerri and Umuahia dialects but it expanded Central Igbo vocabulary by incorporating words from other dialects as well as loanwords. Concomitantly, a written standard was developed.