In organic chemistry, an alkyl is a alkane missing a H.
The term alkyl is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of CnH2n+1. A cycloalkyl is derived from a cycloalkane by removal of a hydrogen atom from a ring and has the general formula CnH2n-1. Typically an alkyl is a part of a larger molecule. In structural formula, the symbol R is used to designate a generic (unspecified) alkyl group. The smallest alkyl group is methyl, with the formula CH3−.
Ethyl is C2H5, as in ethyl alcohol.