What are alicyclic or closed chain or ring compounds? Give examples.

(N/A) Alicyclic (aliphatic cyclic) compounds: These are organic compounds that contain carbon atoms joined in the form of a ring. They resemble aliphatic compounds in their properties. Examples include cyclopropane,cyclohexene,and cyclohexane.
$(b)$ Heterocyclic compounds: These are cyclic compounds in which the ring contains one or more atoms other than carbon (such as $O$,$N$,or $S$). An example is tetrahydrofuran.