Cycloalkanes are to the prefix 'cyclo-' as alkenes are to what prefix?

Cycloalkanes use the prefix “cyclo‑” to show that the carbon chain is closed into a ring. Alkenes are identified by the suffix “‑ene”, which tells you that the molecule contains at least one carbon‑carbon double bond. The naming convention for alkenes therefore relies on the “‑ene” suffix rather than a separate prefix. For example, ethene (C₂H₄) is an alkene whose name ends in “‑ene” to indicate its double bond. Thus, alkenes are to the suffix “‑ene” as cycloalkanes are to the prefix “cyclo‑.