This document discusses alicyclic hydrocarbons, which are cyclic aliphatic hydrocarbons. It covers their nomenclature, wherein the prefix "cyclo-" is added to the name of the corresponding open-chain hydrocarbon. It also discusses their preparation, which involves cyclization reactions to form rings, and conversions between cyclic compounds like alcohols to alkenes. Their reactions are also covered, such as substitution for cycloalkanes and addition for cycloalkenes. Small ring compounds like cyclopropane and cyclobutane undergo ring-opening reactions.