**Core Concept**
Hypochondriac refers to a person who excessively worries about having serious illnesses despite lack of medical evidence. This is a psychiatric condition characterized by persistent, irrational fears of having a disease, often leading to repeated medical consultations and misinterpretation of normal symptoms.

**Why the Correct Answer is Right**
A hypochondriac exhibits persistent and irrational preoccupation with having a serious illness, even when medical evaluations show no evidence of disease. This is distinct from mania, depression, or delirium. The condition involves a distorted perception of bodily symptoms and is rooted in anxiety disorders, particularly illness anxiety disorder. The term "hypochondriac" specifically describes this pattern of health-related anxiety.

**Why Each Wrong Option is Incorrect**
Option B: Mania is characterized by elevated mood, increased energy, grandiosity, and impulsivity — not health-related worries.
Option C: Depression involves low mood, anhedonia, fatigue, and hopelessness, not preoccupation with illness.
Option D: Delirium is a state of acute confusion with fluctuating levels of consciousness, not a preoccupation with health fears.

**Clinical Pearl / High-Yield Fact**
Hypochondriacal individuals often believe they have a disease when tests are normal; they may seek repeated medical opinions and misinterpret minor symptoms. This is now formally known as illness anxiety disorder in DSM-5, and it's crucial to differentiate it from somatic symptom disorder or medical illness.

✓ Correct Answer: A. Hypochondriac