Explain the classification of phenols with examples.

(N/A) Phenols are classified based on the number of hydroxyl $(-OH)$ groups attached to the aromatic ring:
$1$. Monohydric phenols: These contain only one $-OH$ group attached to the benzene ring. Examples include phenol $(C_6H_5OH)$ and $o$-cresol.
$2$. Dihydric phenols: These contain two $-OH$ groups attached to the benzene ring. Examples include catechol ($1,2$-dihydroxybenzene) and resorcinol ($1,3$-dihydroxybenzene).
$3$. Trihydric phenols: These contain three $-OH$ groups attached to the benzene ring. An example is pyrogallol ($1,2,3$-trihydroxybenzene).