sentences:  may not occur word-initially, and only appear in the middle of words, as in 'bird'.There are five tones, "high, mid, low, rising, falling," all of which may occur on simple vowels, for example in "I watered", "I said", "right (direction)".Tone distinguishes words, but also has grammatical functions; for example, the plural of many nouns is formed by changing the tone of the final syllable from low to high, and the perfective aspect of many verbs is similarly formed by changing the tone of the final syllable from low to high.