In organic chemistry, an alkyl substituent is an alkane missing one hydrogen. The term alkyl is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula C_nH_2n+1. A cycloalkyl is derived from a cycloalkane by removal of a hydrogen atom from a ring and has the general formula C_nH_2n-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-.