We don't call this "dumbness." We call this "mutism" -- or you might see "muteness." (the adjective is 'mute') Whether or not mutism is considered a disability (as defined by law) depends on the country where you live.

Hi Kenny, Muteness is a disability on its own and can be a part of larger conditions like autism. If you need information on disability language in (especially US) English, I am both a community tutor here and a disabled woman.

Thank you so much for your help beautiful ladies. Yeah my question was about a kind of disability. Sometimes I put this word on the Google translate and the word /dumbness/ appears like the first option. Moreover, when I was finding out its meaning with other applications the result was the same. But now I got it.

Hi Kenny, If you are asking if someone, whose lack of ability to speak affects their intelligence, the answer is no. Here is why, if a person is born mute, they may not be able to verbally communicate with us, however they are still able to hear, read, and write like us. Or, they can use sign language, which in itself is a language with syntax, context, etc. The same thing goes for someone who might have selective mutism, as they are able to speak but choose not to because they may have anxiety and could fear being shamed, ostracized, or punished. They might have a social anxiety disorder, however that does not mean they lack intelligence. All in all, intelligence is not defined by what is "normal" in society—which, in our case, is defined by what we hear or see. The same thing goes with people who are blind and deaf, they might not have those senses, but they have learned to navigate the world in their own way. Intelligence comes with learning, error, and adapting. I hope I was helpful to you.

Hi Kenny! Dumbness is not a disability, it is usually another word for 'stupid' - it's not a nice word to call someone dumb, as can be seen as nasty. 'He is dumb!' can you explain further what you are referring to when a person can't speak?