Kusaal is classified as follows: ‘Niger-Congo, Atlantic-Congo, Volta-Congo, North, Gur, Central, Northern, Oti-Volta, Western, Southeast, Kusaal’. The language is most closely related to Dagbani and Mampruli, but is also closely related to Frafra (also known by the names Ninkare or Gurune/Gurenne) and Mooré.
Kusaal has two main dialects: the “Eastern Kusaal” dialect, also called the “Agole” Kusaal spoken in Ghana only, in the eastern part of the Kusaal area and the “Western Kusaal” dialect also called the “Tonde” Kusaal spoken in the western area of the Kusaal area in Ghana and across the border in Burkina Faso. Berthelette states in his survey report about Kusaal that the cognate similarity between Tonde and Agole is 84 % (2001, p.18). All words in this dictionary are in the Tonde dialect of Burkina Faso.
A number of studies on the Kusaal language have been produced; however, the majority deal with the Agole and not with the Tonde that is described in the present dictionary. None of these studies goes beyond the sentence level:
- Funke (1922) published a Kusaal wordlist in German (11 pages).
- David and Nancy Spratt, who began their work with the Kusaasi people in 1962 with the Summer Institute of Linguistics (SIL) and later Ghana Institute of Linguistics Literacy and Bible Translation (GILLBT), published The Phonology of Kusal (1968) 154 pages, and Kusal Syntax (1972) 78 pages. Both write-ups are more a sketch than a detailed phonology or grammar of the language. They also published some books in Kusaal for literacy, and translated the New Testament into Kusaal.
- Prost (1979) published Le Kusaal (168 pages). He describes the Burkina Tonde dialect, but his phonology notes are only nine pages long, and he does not write anything about tone.
- Naden has collected a word list with vocabulary mostly from the Eastern Kusaal dialect.
- From 1998 to 2010, Mike and Kathy Steinborn, SIL Burkina Faso, carried out comprehension testing to determine the need for language development in Burkina Kusaal, and began linguistic data collection. They encouraged the Kusaasi to develop their language by training a number of them to help collect linguistic data by working as a team in research and filling in wordlists.
- In March 2010, Urs Niggli was assigned to complete the dictionary using the Toolbox database of 1,800 entries created by the Steinborns.
- More recently two Ghanaian Kusaal mother-tongue scholars from the Eastern Kusaal area have published their Master’s thesis on Eastern Kusaal:

- Agoswin. Aspects of Kusaal Phonology (155 pages) University of Ghana, Legon. 2010.

- Abubakari (Kusaasi), Object-sharing as Symmetric Sharing: Predicate Clefting and Serial Verb Constructions in Kusaal (101 pages) Norway: University of Tromsø. 2011.

Reports on dialect surveys have been written by:
- Berthelette. 2001.
- Steinborn. 2003.

Some information about Kusaal is also to be found in:
- Naden. Work on Gur languages. 1989.
- Manessy. Work on Oti-Volta languages. 1979.