**Core Concept**
Grievous hurt is a legal term defined under the Indian Penal Code (IPC) in the context of criminal liability, specifically relating to bodily injury that results in severe physical damage or long-term disability.

**Why the Correct Answer is Right**
Section 320 of the IPC defines "grievous hurt" as any hurt that causes loss of a limb, loss of sight, loss of hearing, or any other serious physical impairment. It includes injuries that result in permanent disability or significant functional loss. This section is crucial in determining the severity of punishment, as it differentiates between ordinary hurt and grievous hurt, with the former being punishable under Section 324 and the latter under Section 320.

**Why Each Wrong Option is Incorrect**
Option B: Section 318 IPC deals with "voluntarily causing hurt with intent to cause death or grievous hurt," but it does not define grievous hurt itself.
Option C: Section 321 IPC pertains to "voluntarily causing hurt with intent to cause death," not the definition of grievous hurt.
Option D: Section 375 IPC relates to "rape" and is unrelated to the definition of bodily injury or grievous hurt.

**Clinical Pearl / High-Yield Fact**
Remember: "Grievous hurt" under IPC 320 is not just any pain — it must result in **permanent disability** or **loss of a limb, sight, or hearing**. This is a key distinction in forensic cases involving injury assessment.

✓ Correct Answer: A. 320IPC