Four distinct Yupik (or Western Eskimo) languages are spoken along the shores of the Gulf of Alaska, in southwestern Alaska, and on the easternmost tip of Siberia. The Inuit (or Eastern Eskimo) language continuum is spoken in northern Alaska, Canada, and Greenland. Another Eskimo language, the virtually extinct Sirenikski of Siberia, is usually grouped with the Yupik languages although it may actually constitute a third distinct branch.

The sound system of the Yupik branch of Eskimo differs from that of the Inuit branch perhaps principally in the following ways:

1. Yupik has a fourth vowel, the shwa (like the e in the word roses), in addition to the three vowelsa, i, and u found in all Eskimo (and Aleut; Inuit as a result has two kinds of i, that from original iand that originally from the shwa),
2. the Yupik languages have various forms of rhythmic alternation of stressed and unstressed syllables, while such prosodic systems are absent from Inuit,
3. Yupik lacks the consonant assimilation process so common to Inuit (especially as one travels east), and
4. voiceless fricatives are more prominent in Yupik than in Inuit.

As with these phonological differences, the differences in vocabulary between Inuit and any of the Yupik languages is greater than between any two Yupik languages. For example, while Inuit usesumiaq for 'boat', Yupik languages use some form of angyaq; while Yupik uses maklak for 'bearded seal', Inuit uses ugruk. Even words common to both sides will often have a distinctly Yupik version and a distinctly Inuit version. For example, the word for 'leg' is iru in all forms of Yupik and niu in Inuit, though both forms come from the same ancient Eskimo word.

Grammatical structures of Yupik and Inuit are very similar.

The four languages of the Yupik side are Alutiiq (Sugpiaq) on much of the coast of the Gulf of Alaska, Central Yup'ik of Bristol Bay and the Yukon-Kuskokwim delta, Naukanski (in 1999 still spoken by 70 people out of 400 whose ancestors spoke the language) in the East Cape area on the Chukotkan Siberian shore of Bering Strait, and Siberian Yupik on St. Lawrence Island and the facing shore of Chukotka in Siberia. Linguistically, the progression of change goes from Alutiiq to Central Yup'ik up north and over to Naukanski Yupik and then down to Siberian Yupik. Thus, these four languages form a chain via the Inuit-speaking (though formerly Yupik) Seward Peninsula. They are distinct languages with limited mutual intelligibility, and the differences between them are phonological (and morphological) as well as lexical. In addition, there is considerable dialect diversity within Alutiiq and within Central Yup'ik (though not within the other two languages). The northernmost of these languages (Siberian Yupik and Naukanski Yupik) are only slightly closer linguistically to Inuit than is the southernmost (Alutiiq).

The Inuit language is a continuum, or dialect chain, that includes Alaskan Inupiaq and stretches from Unalakleet on Norton Sound across northern Alaska and northern Canada to east Greenland. The change from west to east is marked by the dropping of vestigial Yupik-like features and increasing consonant assimilation (the word for 'thumb' goes from kumlu to kuvlu to kullu) adding to the significant gemination (consonant lengthening) already in Inuit. Lexical change is also encountered and consequently, while two adjacent dialects of Inuit are usually mutually intelligible, speakers from very distant dialects would not easily understand one another.