Molinos Mixtec, another Oto-Manguean language, has a much more complicated system of tone sandhi. The language has three tones (high, mid, or low, or 1, 2, or 3, respectively), and all roots are disyllabic, meaning that there are nine possible combinations of tones for a root or "couplet". The tone combinations are expressed here as a two digit number (high-low is represented as 13). Couplets are also classified into either class A or B, as well as verb or non-verb. A number of specific rules depending on these three factors determine tone change. One example of a rule follows: