Morphologically, languages are often characterized along two dimensions of variation. The first is the number of morphemes per word, ranging from isolating isolating languages like Vietnamese and Cantonese, in which each word generally has one morpheme, to polysynthetic languages like Siberian Yupik ("Eskimo"), in which a polysynthetic single word may have very many morphemes, corresponding to a whole sentence in English. The second dimension is the degree to which morphemes are segmentable, ranging from agglutinative languages like Turkish, in which morphemes have relagglutinative atively clean boundaries, to fusion languages like Russian, in which a single affix fusion may conflate multiple morphemes, like -om in the word stolom (table-SG-INSTR-DECL1), which fuses the distinct morphological categories instrumental, singular, and first declension. Translating between languages with rich morphology requires dealing with structure below the word level, and for this reason modern systems generally use subword models like the wordpiece or BPE models of Section 10.7.1.