Final answer:
The term that denotes rapid speech is tachyphagia. It contrasts with bradyphemia (slow speech), dysphasia (a communication disorder), diaphasia (difficulty in speech due to stress), and paraphasia (incorrect substitution of words or sounds).
Step-by-step explanation:
The word that means rapid speech is tachyphagia. This term is used in medical contexts to describe a pattern of speaking at an unusually fast rate. It can sometimes be a symptom of certain neurological conditions. In contrast, bradyphemia refers to abnormally slow speech.
Dysphasia is a broader term for a language disorder that impacts the ability to communicate, often caused by brain injury or a stroke. Diaphasia is a less common term that might be used to describe difficulty in speech due to emotional stress, while paraphasia involves speech disturbances where one may substitute words or sounds incorrectly.