What is a functional group? Give examples.

(N/A) functional group is defined as an atom or a group of atoms joined in a specific manner,which is responsible for the characteristic chemical properties of organic compounds.
Examples:
$(i)$ $(-OH)$ Hydroxyl group,e.g.,$CH_3OH$
$(ii)$ $(-CHO)$ Aldehyde group,e.g.,$CH_3CHO$
$(iii)$ $(-COOH)$ Carboxylic acid group,e.g.,$CH_3COOH$
Some important functional groups containing carbon-carbon multiple bonds are given in the table below:

Series	Group	Characteristic
Alkene	$ >C=C< $	$C-C$ double bond
Alkyne	$-C \equiv C-$	$C-C$ triple bond
Arene	$C_6H_6$ (Benzene ring)	Six-membered ring with alternate $C=C$ and $C-C$ bonds (aromatic ring)