the vowel length into a difference in quality: Allophony Most varieties have relatively simple patterns of sound alternation (allophony). In many dialects, the voiced consonants are devoiced in word-final position and in consonant clusters: devoices to a voiceless palato-alveolar sibilant , devoices to a voiceless glottal fricative or to a voiceless labialized velar approximant , and devoices to voiceless alveolar lateral fricative . In some dialects, the first consonant in almost any consonant cluster becomes . Some dialects have productive lenition of voiceless consonants into their voiced counterparts between vowels. The nasals are normally assimilated to the place of articulation of a following consonant. The voiceless alveolar lateral affricate is assimilated after and pronounced . Phonotactics Classical Nahuatl and most of the modern varieties have fairly simple phonological systems. They allow only syllables with maximally one initial and one final consonant. Consonant clusters occur only word-medially and over syllable boundaries. Some morphemes have two alternating forms: one with a vowel i to prevent consonant clusters and one without it. For example, the absolutive suffix has the variant forms -tli (used after consonants) and -tl (used after vowels). Some modern varieties, however, have formed complex clusters from vowel loss. Others have contracted syllable sequences, causing accents to shift or vowels to become long. Stress Most Nahuatl dialects have stress on the penultimate syllable of a word. In Mexicanero from Durango, many unstressed syllables have disappeared from words, and the placement of syllable stress has become phonemic. Morphology and syntax The Nahuatl languages are agglutinative, polysynthetic languages that make extensive use of compounding, incorporation and derivation. That is, they can add many different prefixes and suffixes to a root until very long words are formed, and a single word can constitute an entire sentence. The following verb shows how the verb is marked for subject, patient, object, and indirect object: Nouns The Nahuatl noun has a relatively complex structure. The only obligatory inflections are for number (singular and plural) and possession (whether the noun is possessed, as is indicated by a prefix meaning 'my', 'your', etc.). Nahuatl has neither case nor gender, but Classical Nahuatl and some modern dialects distinguish between animate and inanimate nouns. In Classical Nahuatl the animacy distinction manifested with respect to pluralization, as only animate nouns could take a plural form, and all inanimate nouns were uncountable (as the words bread and money are uncountable in English). Now,