In the case of coordinate covalent bond, the sharing of electron comes from only one species or atom which means only atom shares electron but other doesn't. It is one sided sharing. It is formed betn electron rich species called donors and electron deficient species or atoms called acceptors.
covalent bond is represented by "---" or solid line whereas coordinate covalent bond is represented by solid line with an arrow head "------>" pointing from donors to acceptors.
example: During the formation of ozone (O=O-->O) this structure bond formation takes place. It shows that 2 oxygen atoms are having double covalent bond(O=O) and (O-->O) represents coordinate bond. In (O-->O) first oxygen is giving or sharing 2 electrons but other oxygen is not giving or sharing electrons.
