stressed syllables have a higher pitch than unstressed syllables, whereas in Russian, stressed syllables have a lower pitch. Types Register tones and contour tones In many Bantu languages, tones are distinguished by their pitch level relative to each other. In multisyllable words, a single tone may be carried by the entire word rather than a different tone on each syllable. Often, grammatical information, such as past versus present, "I" versus "you", or positive versus negative, is conveyed solely by tone. In the most widely spoken tonal language, Mandarin Chinese, tones are distinguished by their distinctive shape, known as contour, with each tone having a different internal pattern of rising and falling pitch. Many words, especially monosyllabic ones, are differentiated solely by tone. In a multisyllabic word, each syllable often carries its own tone. Unlike in Bantu systems, tone plays little role in the grammar of modern standard Chinese, though the tones descend from features in Old Chinese that had morphological significance (such as changing a verb to a noun or vice versa). Most tonal languages have a combination of register and contour tones. Tone is typical of languages including Kra–Dai, Vietic, Sino-Tibetan, Afroasiatic, Khoisan, Niger-Congo and Nilo-Saharan languages. Most tonal languages combine both register and contour tones, such as Cantonese, which produces three varieties of contour tone at three different pitch levels, and the Omotic (Afroasiatic) language Bench, which employs five level tones and one or two rising tones across levels. Most varieties of Chinese use contour tones, where the distinguishing feature of the tones are their shifts in pitch (that is, the pitch is a contour), such as rising, falling, dipping, or level. Most Bantu languages (except northwestern Bantu) on the other hand, have simpler tone systems usually with high, low and one or two contour tone (usually in long vowels). In such systems there is a default tone, usually low in a two-tone system or mid in a three-tone system, that is more common and less salient than other tones. There are also languages that combine relative-pitch and contour tones, such as many Kru languages and other Niger-Congo languages of West Africa. Falling tones tend to fall further than rising tones rise; high–low tones are common, whereas low–high tones are quite rare. A language with contour tones will also generally have as many or more falling tones than rising tones. However, exceptions are not unheard of; Mpi, for