Different verb tenses have different tonal patterns. The tones of verbs are made more complicated by the fact that some verbs have a high tone on the first syllable of the root, while others do not, and also by the fact that the sequence HH generally becomes HL by a rule called Meeussen's rule. Thus "asóma" means 'he reads', but when the toneless prefix "a-" 'he/she' is replaced by the high-toned prefix "bá-" 'they', instead of "básóma" it becomes "básomá" 'they read'. The tones of verbs in relative clauses and in negative sentences differ from those in ordinary positive sentences and the addition of an object-marker such as "mu" 'him' adds further complications.