Asụsụ Igbo is a language spoken in Nigeria by around 20-25 million people, the Igbo, especially in the southeastern region once identified as Biafra and parts of Southsouthern region of Nigeria. The language was used by John Goldsmith as an example to justify deviating from the classical linear model of phonology as laid out in The Sound Pattern of English. It is written in the Roman script. There is also the Nsibidi alphabet which is used by the Ekpe society. Igbo is a tonal language, like Yoruba and Chinese. There are hundreds of different dialects and Igboid languages that the Igbo language comprises such as Ikwerre Enuani (linguistics) and Ekpeye dialects.
Igbo has a number of dialects, distinguished by accent or orthography but almost universally mutually intelligible, including the Idemili Igbo dialect (the version used in Chinua Achebe's epic novel, Things Fall Apart), Bende, Owerri, Ngwa, Umuahia, Nnewi, Onitsha, Awka, Abiriba, Arochukwu, Nsukka, Mbaise, Abba, Ohafia, Ika, Wawa, Okigwe Ukwa/Ndoki and Enuani. It is considered to be a dialect continuum. There is apparently a degree of dialect levelling occurring.
The wide variety of spoken dialects has made agreeing a standardised orthography and dialect of the Igbo language very difficult. The current Onwu orthography, a compromise between the older Lepsius orthographyInternational Institute of African Languages and Cultures (IIALC), was agreed in 1962. and a newer orthography advocated by the Central Igbo, the dialect form gaining widest acceptance, is based on the dialects of two members of the Ezinihitte group of Igbo in Central Owerri Province between the towns of Owerri and Umuahia, Eastern Nigeria. From its proposal as a literary form in 1939 by Dr. Ida C. Ward, it was gradually accepted by missionaries, writers, and publishers across the region. In 1972, the Society for Promoting Igbo Language and Cultureloan words. (SPILC), a nationalist organisation which saw Central Igbo as an imperialist exercise, set up a Standardisation Committee to extend Central Igbo to be a more inclusive language. Standard Igbo aims to cross-pollinate Central Igbo with words from Igbo dialects from outside the "Central" areas, and with the adoption of Igbo is both spoken and written language mainly in southeastern Nigeria but this usage also extends beyond these confines to southsouthern Nigeria covering some parts of Rivers and Delta States where the Ikweres, Anioma and others are geographically situated. In Anioma (Among the Eneani) especially, the Igbo language is still referred to as "Asusu Igbo" and retains much of Igbo words and idiomatic expressions.