Here's why:

* Alkene Definition: Alkenes are hydrocarbons that contain a carbon-carbon double bond.

* Styrene Structure: Styrene has the chemical formula C8H8. Its structure contains a benzene ring (a cyclic aromatic system) attached to a vinyl group (-CH=CH2). The vinyl group is where the carbon-carbon double bond resides.

Therefore, due to the presence of the carbon-carbon double bond in the vinyl group, styrene qualifies as an alkene.