Final answer:
The suffix for alkene is -ene and for alkyne is -yne.
Step-by-step explanation:
The suffix when naming an alkene or alkyne is determined by the type of bond present in the molecule.
For alkene, which has a double bond, the suffix -ane in the name of the corresponding alkane is replaced with -ene. For example, ethane becomes ethene when it has a double bond.
For alkyne, which has a triple bond, the suffix -ane in the name of the corresponding alkane is replaced with -yne. For example, ethane becomes ethyne when it has a triple bond.