In the definition, we divide hydrocarbons into two categories according to the carbon skeleton in the molecule. One is open chain hydrocarbon, and the other is cyclic hydrocarbon. Alkanes refer to open-chain saturated hydrocarbons. In the first classification, cycloalkanes have been separated from the concept of alkanes.
Because cycloalkane is not an open chain hydrocarbon, it cannot be said that cycloalkane belongs to alkane.