There are four main conditions for an invention to be patentable:

• Novelty: The invention must have objective newness and must not already be known in an accessible form from anywhere in the world.
• Inventive step: An invention must involve an inventive step. This means that it must lie beyond what is obvious to an average professional in the field.
• Industrial applicability: The invention must be industrially applicable and the inventor must be able to describe how others can reproduce the invention.
• Within patent law: The invention must not be of such a nature as to be excluded from patentability in patent law.

An invention may lose its character of novelty in several ways, for example, by

• Publication of an article
• Publication of an exam project
• Submission of a PhD thesis for assessment
• Disclosure of an abstract
• Talk/lecture for an indeterminate group (can be quite small – as small as one person – if only one person in the group is not bound by the obligation to maintain the secrecy of the information)
• Scientific posters
• Disclosing or mentioning the invention to an indeterminate group
• Sale
• Careless storage which makes the invention available to an indeterminate group
• Television broadcast
• Radio broadcast

An invention’s character of novelty is not damaged by, for example:

• Mentioning under secrecy
• Showing under secrecy
• Submission of a confidential manuscript
• Submission of a confidential application for support
• Confidential conversations with advisers

In practice, submission of confidential manuscripts alone rarely causes major problems the reason being that it will often take some time from the submission of the manuscript to its publication. A patent application will normally be drawn up and submitted during this time period.

An invention involves an inventive step when it differs significantly from the closest related technique known on the filing date of the patent application. As evidence of an inventive step, reference can be made to the invention achieving specific technical advantages such as higher production speed or greater benefit – for example, illustrated by comparison trials.

The requirement of industrial applicability means that the invention can be used industrially. Industrial use is not confined to industry in the strict sense but also includes use in agriculture, forestry and fishing.

Exceptions in the patent law are relatively few and specific. There are, however, certain types of inventions that cannot be patented. The patent laws of respective countries contain regulations that stipulate the rules for this. For example, certain methods for therapeutic and surgical treatment are excluded from patenting in Europe but not in the U.S.A.