Hyperbole is deliberate overstatement, offered without any expectation of being believed literally. The exaggeration is understood by both parties, which is precisely what separates it from a false claim: nobody is deceived, because nobody was meant to be.
Its purpose is to convey the scale of a feeling when the literal facts would understate it.
Macbeth, after the murder: “Will all great Neptune's ocean wash this blood clean from my hand? No; this my hand will rather the multitudinous seas incarnadine.” He does not mean that his hand would discolour the Atlantic. He means the guilt will not come off.
Hyperbole fails the moment the audience is unsure whether it was meant literally. At that point it stops being a figure and becomes a claim.
Hyperbole depends entirely on a shared understanding that it is not literal, and that understanding is fragile. It survives easily in poetry, conversation and comedy, where tone carries the signal. It survives badly in anything that might be quoted, excerpted or translated — contexts where the tone is stripped away and only the proposition remains.
This is why the device is risky in argument specifically. A hyperbolic figure in a persuasive piece can be quoted back as a factual assertion, and the writer is then defending a claim they never made. Worse, an audience that catches one overstatement will begin discounting the accurate statements around it.
There is also a cumulative cost. Hyperbole works by exceeding the normal register, so a writer who uses it constantly has no register left to exceed. The standard failure is a piece in which everything is unprecedented, catastrophic or extraordinary, and the reader has stopped being able to tell which of those was meant.
