Univalent groups derived from alkanes by removal of a hydrogen atom from any carbon atom $\ce{–C_{n}H_{2n+1}}$. The groups derived by removal of a hydrogen atom from a terminal carbon atom of unbranched alkanes form a subclass of normal alkyl ($n$-alkyl) groups $\ce{H(CH2)_{n}}$. The groups $\ce{RCH2}$, $\ce{R2CH}$ ($\ce{R \neq H}$), and $\ce{R3C}$ ($\ce{R \neq H}$) are primary, secondary and tertiary alkyl groups, respectively.