every year, both in Brazil and Peru. Those books employ a specially devised phonetic writing system using conventions similar to those found in Portuguese (except for K instead of C and the letter Ñ instead of NH) instead of the more complex scientific notation found, for instance, at the Language Museum. In school Ticuna is taught formally. Children in schools typically in areas of Catholic Missionaries are also taught either Portuguese or Spanish as well. Linguistic structure Ticuna is a fairly isolating language morphologically, meaning that most words consist of just one morpheme. However, Ticuna words usually have more than one syllable, unlike isolating languages such as Vietnamese. Ticuna is an unusually tonal language for South America, with over 10 mostly contour tones. Tones are only indicated orthographically, with diacritics, when confusion is likely. The six vowels may be nasal or laryngealized; consonants may also be glottalized. Glottal stop is spelled x, and the sixth vowel ü. Typologically, Ticuna word order is subject–verb–object (SVO), though unusually this can vary within the language. Research has indicated isolated tonal languages with complex tones are more likely to occur in regions of higher humidity and higher mean average temperature because it is believed the vocal folds can produce less consistent tones in colder, drier air. Ticuna was one of the languages of focus in this study due to its prevalence—and complexity—of tones. Classification Some have tentatively associated the Ticuna language within the proposals of the macro-arawakano or with macro-tukano stocks, although these classifications are highly speculative given the lack of evidence. A more recent hypothesis has linked Yuri-Ticuna with the Saliban and Hoti languages in the Duho stock. However, the linguistic consensus is that Ticuna may actually be a language isolate in its present-day situation, since Yuri is extinct. Phonology Vowels Vowels qualities are . Vowels may be nasalized and/or show creaky voice, under which tones are lowered. There are diphthongs and that carry a single tone, contrasting with vowel sequences and that carry two tones. Tones Ticuna has one of the largest tone inventories in the world with 8–12 phonemic tones depending on the dialect. Consonants The consonants of Ticuna consist of the following phonemes: Natively, Ticuna has no lateral or uvular consonants, although /l/ is found in some spanish loanwords. The affricate (spelled "y") may be pronounced as , and also , but only before the vowel . A central vowel