Explain the classification of amine compounds with suitable examples.

(N/A) Amines are classified based on the number of hydrogen atoms replaced by alkyl or aryl groups in an ammonia molecule $(NH_3)$.
$(i)$ Primary $(1^{\circ})$ amines: When one hydrogen atom of ammonia is replaced by an alkyl $(R)$ or aryl $(Ar)$ group,we get $RNH_2$ or $ArNH_2$. Example: $CH_3CH_2NH_2$ (Ethanamine).
$(ii)$ Secondary $(2^{\circ})$ amines: When two hydrogen atoms of ammonia are replaced by alkyl or aryl groups,we get $R_2NH$. Example: $CH_3NHCH_3$ ($N$-methylmethanamine).
$(iii)$ Tertiary $(3^{\circ})$ amines: When all three hydrogen atoms of ammonia are replaced by alkyl or aryl groups,we get $R_3N$. Example: $(CH_3)_3N$ ($N,N$-dimethylmethanamine).
Aryl amines are those where the nitrogen atom is directly attached to an aromatic ring. Example: $C_6H_5NH_2$ (Aniline/Aminobenzene).
Amines are 'simple' if all alkyl/aryl groups are the same,and 'mixed' if they are different.