The suffix in ethanol is used to Define Which functional Group

Explanation

To determine the functional group defined by the suffix in ethanol, we can break down the name "ethanol" into its components and analyze them step by step.

### Step-by-Step Solution:

1. **Identify the Components of the Name**:
- The name "ethanol" can be divided into three parts: "eth", "an", and "ol".
- Here, "eth" refers to the number of carbon atoms, "an" indicates the type of carbon-carbon bonds, and "ol" is the suffix that defines the functional group.

2. **Understanding the Root "eth"**:
- The prefix "eth" signifies that there are two carbon atoms in the molecule. This is derived from the alkane series where "eth" corresponds to C2 (two carbon atoms).

3. **Analyzing the Suffix "an"**:
- The suffix "an" indicates that there are single bonds between the carbon atoms (C-C single bond). This is characteristic of alkanes.

4. **Identifying the Suffix "ol"**:
- The suffix "ol" is specifically used to denote alcohols. This indicates the presence of a hydroxyl group (-OH) in the molecule.

5. **Combining the Information**:
- In ethanol (C2H5OH), we see that it contains two carbon atoms (from "eth"), a single bond (from "an"), and a hydroxyl group (from "ol").
- Therefore, the functional group present in ethanol is the hydroxyl group (-OH), which is characteristic of alcohols.

6. **Conclusion**:
- The suffix "ol" in ethanol defines the functional group of alcohols.

### Final Answer:
The suffix in ethanol is used to define the functional group of alcohols.