For a compound to be aromatic it must have `(4n + 2) pi` electrons.

Answer

### Step-by-Step Solution:

1. **Understanding Aromatic Compounds**:
Aromatic compounds are a special class of cyclic compounds that have unique stability and reactivity due to their electronic structure.

2. **Hückel's Rule**:
For a compound to be classified as aromatic, it must satisfy Hückel's rule, which states that the compound must have `(4n + 2)` π (pi) electrons, where `n` is a non-negative integer (0, 1, 2, ...). This means that the total number of π electrons in the cyclic, planar structure must equal 2, 6, 10, 14, etc.

3. **Planarity**:
The molecule must be planar, meaning all the atoms in the ring must lie in the same plane. This allows for effective overlap of p-orbitals, which is essential for delocalization of π electrons.

4. **Conjugation**:
The compound must exhibit conjugation, which means there should be alternating single and double bonds in the ring structure. This alternation allows for the delocalization of π electrons across the entire molecule.

5. **Conclusion**:
To summarize, for a compound to be aromatic, it must meet the following conditions:
- It must be cyclic.
- It must be planar.
- It must have conjugation (alternating double bonds).
- It must follow Hückel's rule of having `(4n + 2)` π electrons.