What functional group does the term "hydroxy" refer to?

The term "hydroxy" refers specifically to the functional group consisting of an oxygen atom bonded to a hydrogen atom, denoted as -OH. This functional group is commonly found in alcohols and phenols, and it plays a significant role in the chemical behavior of compounds that contain it. For instance, the presence of the hydroxy group typically contributes to the polarity of a molecule, influencing its solubility in water and its reactivity.

In contrast, the other functional groups listed do not correspond to the term "hydroxy." The amino group (-NH₂) is associated with amines, the carboxylic acid group (-COOH) is related to acids, and the aldehyde group (-CHO) is a characteristic of aldehydes. Each of these groups has distinct properties and reactivities that differentiate them from the hydroxy group.