What is a patent? 19/7/02. By Deirdre Janson-Smith A patent is a licence granted to an inventor, which gives the inventor the legal right to stop anyone else from making, using or selling the invention without his or her permission.

Patents generally cover technological advances – new products and processes. To be patented, an invention must meet three criteria: it must be novel, innovative and useful. To test this, the person applying for a patent must publish a description and instructions that could enable someone else to make and use the product or carry out the process.

Once a patent is granted, the invention becomes the inventor's property – like any property, it can be bought and sold, rented or hired. A patent normally lasts 20 years, after which anyone can use the invention.

An invention cannot be patented if it is simply a discovery. Neither can it be a scientific theory or mathematical method; a literary, dramatic or artistic work; a scheme or method for performing a mental act, playing a game or doing business; the presentation of information; or a computer program. (Rights to many of these are covered by copyright law.)

It not possible to get a patent for 'inventing' a new animal or plant variety by traditional breeding methods; nor for a new surgical or therapeutic method of treatment of either humans or animals, or a method of diagnosis. However, genetically engineered plants and animals can be patented. So can naturally-occurring chemical codes and cellular substances – like genes or hormones – as long as they are isolated from the body by novel technical means, and a use is clearly specified for them.

Some processes and products may be declared non-patentable if their use would be 'contrary to the public order or morality'. British law, for example, bans the patenting of any techniques to clone human embryos modify human germline cells or use human embryos for industrial and commercial purposes. (Such bans have an ancient history. Queen Elizabeth I refused to grant a patent in 1596 to Sir John Harrington on his design for a water closet, on the grounds of propriety.)

Patents are territorial rights. The patents issues by the UK Patent Office only grant protection within the United Kingdom and over imports into the United Kingdom. However, Britain has also signed up to the European Patent Convention, so inventions patented in one of 19 other European countries are also protected here, and vice versa. Under the 1995 Trade-Related Intellectual Property Rights (TRIPS) agreement, similar patent rules are supposed to be in place across almost the entire world.