What functional group characterizes amines?

Amines are characterized by the presence of the amino functional group, which is represented as -NH2. This group consists of a nitrogen atom bonded to two hydrogen atoms. Amines can be classified into primary, secondary, and tertiary based on the number of carbon-containing groups attached to the nitrogen atom, but the defining feature of all amines is the presence of the -NH2 unit.

The other functional groups listed in the options represent different types of compounds. The -CONH2 group, for example, corresponds to amides, which are derived from carboxylic acids. The -COOH group indicates the presence of carboxylic acids, known for their acidic properties. Lastly, the -OCH3 group denotes an ether or methoxy group, which is characterized by an oxygen atom connected to a methyl group. These groups do not have the defining features of amines, thereby affirming that the -NH2 group is what distinctly characterizes them.