## **Core Concept**
Relative risk (RR), also known as the risk ratio, is a measure used in epidemiology to compare the risk of a certain event (such as developing a disease) occurring in one group with the risk of the same event occurring in another group. It is essentially a ratio of the probability of an event occurring in the exposed group versus the non-exposed group.

## **Why the Correct Answer is Right**
The correct answer, , indicates that the relative risk measures the **risk of disease in the exposed group compared to the non-exposed group**. This is precisely the definition of relative risk. It quantifies the strength of association between a particular risk factor and the disease by comparing the risk of disease among those exposed to the risk factor to the risk among those not exposed.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately describe what relative risk measures.
- **Option B:** This option is incorrect because, although it mentions comparing risks, it does not specify that it is about the risk of disease in exposed vs. non-exposed groups.
- **Option C:** This option is incorrect because it refers to a different epidemiological measure. The odds ratio is used in case-control studies to estimate the strength of association between a risk factor and a disease.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that a **relative risk of 1** indicates **no difference in risk** between the exposed and non-exposed groups. A **relative risk greater than 1** suggests an **increased risk** of the disease in the exposed group, while a **relative risk less than 1** suggests a **reduced risk** or **protective effect**.

## **Correct Answer:** . Risk of disease in exposed group compared to non-exposed group