A renewable resource is a natural resource which can be replenished through means of biological reproduction of other naturally occurring processes. On the other hand, a non-renewable resource is a natural...

Perennial rivers are those rivers which exhibit a continuous flow of water throughout the year except during extreme drought. On the other hand, non-perennial rivers are those rivers which have no flow for at...

Delta is a sedimentary deposit formed at mouth of some rivers. It is usually triangular in shape. On the other hand, an estuary is a semi-enclosed body of water where fresh water meets the ocean.

A submarine is a vessel that is capable of propelling itself underwater as well as at the surface of water. U-boats are submarines of Germany which were designed to be used in world wars I and II