What do you mean by alkene? Give its general formula and two examples.

(N/A) Alkenes are unsaturated hydrocarbons containing at least one carbon-carbon double bond $(C=C)$.
The general formula for alkenes is $C_{n}H_{2n}$,where $n$ is the number of carbon atoms $(n \geq 2)$.
Alkenes have two hydrogen atoms fewer than the corresponding alkanes.

Name $(IUPAC)$	Structure and Molecular formula
Ethene	$CH_{2}=CH_{2}$ $(C_{2}H_{4})$
Propene	$CH_{3}-CH=CH_{2}$ $(C_{3}H_{6})$