Aside from all physical possibilities of muteness, a child born completely or very nearly deaf in both ears has higher odds of also being unable to speak. Humans learn the pronunciation and manners of language by what they hear, so children who lack the ability to hear can also lack the ability to talk. This does not mean they are actually mute, or deaf-mute, but it means that they are effectively mute because of the inability to form the noises they can make into words.
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