**Core Concept**
Incidence is a fundamental epidemiological measure used to describe the frequency of new cases of a disease within a defined population over a specified period. It is an essential metric for understanding the burden and spread of diseases.

**Why the Correct Answer is Right**
Incidence measures the rate of new disease occurrence, which is calculated as the number of new cases of a disease divided by the number of individuals at risk in the population over a specific time interval. This helps in assessing the impact of a disease on a population and evaluating the effectiveness of interventions. Incidence is often expressed as a rate per 1,000 or 100,000 individuals per year.

**Why Each Wrong Option is Incorrect**
**Option A:** Prevalence is the total number of cases of a disease in a population at a given time, including both new and existing cases. It does not measure the rate of new disease occurrence.
**Option B:** Morbidity rate is a broader term that refers to the incidence of disease in a population, but it can also include other measures of disease burden, such as prevalence.
**Option C:** Mortality rate is the number of deaths from a specific disease or cause in a population over a specified period, which is distinct from the incidence of disease.

**Clinical Pearl / High-Yield Fact**
Remember the mnemonic "IDEAS" to differentiate between incidence (I), prevalence (D), morbidity (E), and mortality (A) rates: "I'm Dying, Eating, and Always Sick".

**Correct Answer: C. Mortality rate is the number of deaths from a specific disease or cause in a population over a specified period, which is distinct from the incidence of disease.