What is Patent?
A patent is a legal document granted by the government giving an inventor the exclusive right to make, use, and sell an invention for a specified number of years. Patents are also available for significant improvements on previously invented items. The goal of the patent system is to encourage inventors to advance the state of technology by awarding them special rights to benefit from their inventions. Books, movies, and works of art cannot be patented, but protection is available for such items under the law of copyright. Patent law is one branch of the larger legal field known as intellectual property, which also includes trademark and copyright law. Patent law centers usually go about the concept of novelty and inventive step (or lack of obviousness). The right which they accord is to prevent all others, not just imitators but even independent devisors of the same idea from using the invention for the duration of the patent. The special potential of a patent is that it may be used to prevent all
others from including any form of the invention in their product and services. A patent thus poses serious difficulties for its competitors. This is why patents are not easily available for all industrial improvements but only to those that are judged to qualify as a patentable invention.

What is Patentable?
To qualify for a patent, the invention must meet three basic criteria:
1. It must be novel, meaning that the invention did not previously exist.
2. The invention must be non-obvious, which means that the invention must be a significant improvement to existing technology. Simple changes to previously known devices do not comprise a patentable invention.
3. The proposed invention must be useful. Legal experts commonly interpret this to mean that no patent will be granted for inventions that can only be used for an illegal or immoral purpose.
Some types of discoveries are not patentable. No one can obtain a patent on a law of nature or a scientific principle even if he or she is the first one to discover it. For example, Isaac Newton could not have obtained a patent on the laws of gravity, and Albert Einstein could not have patented his formula for relativity, E=mc2.

What is not Patentable?
Some inventions cannot be patented. Under Indian law, the following are non-patentable (as mentioned under section 3 and 5 of the Indian Patents Act, 1970):-
An invention, which is frivolous or which claims anything contrary to well established natural laws. An invention the primary or intended use of which would be contrary to law or morality or injurious to public health. The mere discovery of a scientific principle or the formulation of an abstract theory.

The mere discovery of any new property or new use for a known substance or of the mere use of a known process, machine or apparatus unless such known process results in a new product or employs at least one new reactant. A substance obtained by a mere admixture resulting only in the aggregation of the properties of the components thereof or a process for producing such substance The mere arrangement or re-arrangement or duplication of known devices each functioning independently of one another in a known way. A method or a process of testing applicable during the process of manufacture for rendering the machine, apparatus or other equipment more efficient or for the improvement or restoration of the existing machine, apparatus or other equipment or for the improvement or control of manufacture. A method of agriculture or horticulture. Any process for the medicinal, surgical, curative, prophylactic or other treatment of human being or any process for a similar treatment of animals or plants to render them free of disease or to increase their economic value or that of their products.

No Patent shall be granted in respect of an invention relating to atomic energy. Claiming substances intended for use, or capable of being used as food or as medicine or drug related to a substance prepared or produced by chemical processes (including alloys, optical glass, semiconductor and intermetallic compounds), no patent shall be granted in respect of claims for the substances themselves, but claims for the methods or processes of manufacture shall be patentable. The criteria under the US laws are also quite similar to above.