These words all refer either to an inability or unwillingness to speak or produce sound or to be intelligible. Speechless often refers to a transitory inability to speak because of shock or powerful emotions: struck speechless by the news. In a similar way one is often tongue-tied by nervousness or embarrassment and simply cannot get the words out: He stood tongue-tied before the huge audience. Sometimes speechless can indicate an impairment of speech functions: The brain damage resulted in an aphasia that rendered her husband totally speechless . Much more commonly, however, dumb or mute refer to any such sort of permanent inability to speak. Dumb may refer to this inability when caused by some defect of the speech organs, whereas mute is often the word of choice when the inability results, instead, from never having heard speech sounds, as in deafness sustained since infancy: a child who was dumb because of deformed vocal cords; a technique for teaching mute children to speak in spite of their deafness. Sometimes mute is substituted for dumb , regardless of cause, since dumb can also apply informally as a pejorative word for mental dullness. This linking of two unrelated deprivations may once have been deliberate but it is now felt to be both inaccurate and cruel. Dumb can also function like speechless to indicate a temporary loss of speech, though it can refer as well to an inability to make any sort of sound because of shock or emotion: dumb with fright. In this context, mute more often refers to a deliberate refusal to speak: She answered his question with mute contempt; a prisoner who stolidly remained mute under the most excruciating tortures they could devise. When the reference is not to people, dumb refers to a possibly natural or normal incapacity for speech but not necessarily to an inability to produce sound: dumb animals. In a similar situation, mute may refer to complete soundlessness: the mute hush of the forest at dusk. The verb form of the word is of interest here, since it refers to altered or subdued sound: muted trumpets.

Inarticulate can be a vague and confusing word, since it can refer to what is soundless, speechless , unintelligible, confused or halting ?at times rather like tongue-tied , which is far more colloquial. Only context can make clear which notion is intended: His mouth worked to form words, but he remained completely inarticulate ; gasping in inarticulate fright; lines in the play that were lost because of inarticulate mumbling; an inarticulate presentation of his idea; simple lessons that help stutters to be less inarticulate . Incoherent can sometimes be substituted for speechless , but most often it clearly implies confused statements or halting speech: an incoherent essay filled with circumlocution and digression; stammered accusations and incoherent outcries.