What is primary $(1^{\circ})$,secondary $(2^{\circ})$,tertiary $(3^{\circ})$ and quaternary $(4^{\circ})$ carbon? Give its example.

(N/A) The classification of a carbon atom as primary $(1^{\circ})$,secondary $(2^{\circ})$,tertiary $(3^{\circ})$,or quaternary $(4^{\circ})$ depends on the number of other carbon atoms directly attached to it.
$1^{\circ}$ (Primary): $A$ carbon atom attached to no other carbon atom (as in methane) or only one other carbon atom (as in ethane) is called a primary carbon.
$2^{\circ}$ (Secondary): $A$ carbon atom attached to two other carbon atoms is known as a secondary carbon.
$3^{\circ}$ (Tertiary): $A$ carbon atom attached to three other carbon atoms is known as a tertiary carbon.
$4^{\circ}$ (Quaternary): $A$ carbon atom attached to four other carbon atoms is known as a quaternary carbon.
Examples:

Structure	Forms of carbon
$H_3C-CH(CH_3)-CH_2-CH_3$ ($2$-Methylbutane)	Terminal $-CH_3$ groups are $1^{\circ}$. The $CH$ carbon is $3^{\circ}$ (attached to $3$ carbons). The $-CH_2-$ carbon is $2^{\circ}$ (attached to $2$ carbons).
$C(CH_3)_4$ ($2$,$2$-Dimethylpropane)	The central carbon is $4^{\circ}$ (attached to $4$ carbons). The four terminal $-CH_3$ carbons are $1^{\circ}$.