What is a functional group? Give examples of four different functional groups.

Explanation

### Step-by-Step Solution:

1. **Definition of Functional Group**:
A functional group is a specific group of atoms or bonds within a molecule that is responsible for the characteristic chemical reactions of that molecule. It determines the properties and reactions of the compound.

2. **Examples of Functional Groups**:
- **Aldehyde**: The functional group for aldehydes is represented as -CHO. Aldehydes are characterized by the presence of a carbonyl group (C=O) bonded to a hydrogen atom.
- **Alcohol**: The functional group for alcohols is represented as -OH. Alcohols contain a hydroxyl group, which is an oxygen atom bonded to a hydrogen atom.
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