Sahaptin, or Ichishkíin Sínwit (literally, "this language"), is a Plateau Penutian language spoken in south-central Washington and northern Oregon. This dictionary documents the dialect of Sahaptin that is spoken by the Yakama people. Ichishkíin Sínwit Yakama / Yakima Sahaptin Dictionary is the first modern published dictionary of any Sahaptin dialect.

The dictionary is divided into three sections: a Sahaptin-English section; an English-Sahaptin section; and a section listing roots used in the formation of Sahaptin words. The Sahaptin-English section contains approximately 3,500 headwords, over 4,500 example sentences, more than 100 images, and over 9,200 sound files available online.

Copious cross-references alert readers to related words elsewhere in the Sahaptin-English section. The English-Sahaptin and roots sections serve as indices to the Sahaptin-English section. In the English-Sahaptin section, users can look up the Sahaptin equivalents of English words. In the root section, users can see words from different parts of the dictionary that share the same component of meaning.

The dictionary also contains essays by noted Plateau linguist Bruce Rigsby (professor emeritus, University of Queensland) on the histories and current usage of the terms "Sahaptin" and "Yakima / Yakama."