Sentence:  In the introduction to this paper, it was stated that the asymmetric <WSD>tonology</WSD> of Yorùbá in no way marked the language out as unique. To help set the language in a wider context, some aspects of the <WSD>tonology</WSD> of two related languages are now described. One of these, like Yorùbá, has three surface tone heights, while the other has four. It is shown that the <WSD>tonologies</WSD> of these languages are also consistent with the hypothesis that 'Low Tone', in West Africa, is not [L]. 
Meaning of the word marked with <WSD> tags:  The system of rules governing tones in a particular language.