Monosyllabic morphemes carry one of two tones, high and low. Bimoraic roots carry one of six tones: high-level, high-mid (or "high falling"), mid-low (or "mid"), low-mid dipping/rising, high falling (or "falling"), and low falling (or "low"). Low falling and low-mid are accompanied by a breathy voice phonation, the other four with a clear phonation. The high and low falling tones form a natural class, triggering for example a high tone on the suffix -si, whereas the other four root tones trigger a low tone on -si.