The definitions section of the Patent Act specify that an invention is any new and useful art, process, machine, manufacture or composition of matter, or any new and useful improvement in any art, process, machine, manufacture or composition of matter. No patent may issue for a mere scientific principle or abstract theorem (section 27(8) of the Act refers). Some examples of patentable subject matter are: a new microbiological process for making an antibiotic; a new internal combustion engine; or an improved snow shovel. Examples of subject matter which are not patentable include: methods of medical treatment; computer programs per se; or professional methods e.g. a method of speech therapy. It is important to note that in the case of an improvement, the patentee does not obtain the right to make or sell the original invention nor does the patentee of the original invention have the right to make or sell the improvement (section 32 of the Act refers).

An invention must have the following attributes:
(a) it must be novel;
(b) it must possess utility; and
(c) it must be non-obvious.

The first requirement dictates that nothing like the invention must have come before i.e. the subject matter must not have been described in a patent or other publication more than one year before the filing date (see s. 28.2 of the Act).

The second requirement stipulates that someone skilled in the art must be able to take the patent and construct an apparatus that would answer some beneficial purpose. Finally, the third requirement, which is statutorily defined in section 28.3 of the Act, demands that there be some inventive ingenuity evident i.e. the invention must not appear to be obvious to a workman skilled in the particular art.

The document in which an invention is described is known as the patent specification. The specification includes a disclosure, which may include drawings, and one or more claims. The disclosure and drawings correctly and fully describe the invention and its operation or use as contemplated by the inventor, while the claims define distinctly and in explicit terms the subject matter of the invention for which an exclusive privilege is claimed. Claims have been described as a fence surrounding the patentee's property. The fence must not encroach on another's property; that is, valid claims cannot cover subject matter that is either in the public domain or that belongs to another party. A claim may be held invalid if it is overly broad and fails to distinguish the invention from previously known inventions. On the other hand, a claim may be constructed too narrowly and thereby inadequately protect the invention, allowing others to cicumvent it.

Under section 42 of the Patent Act, the grant of a patent gives the patentee the exclusive right to manufacture, use and sell an invention for the term of patent. The term of the patent is defined in section 44 of the Act as twenty years from the filing date. Each claim is a separate monopoly. A patent is infringed if a third party encroaches on one or more claims. Under Section 55(2) of the Patent Act, a person who infringes a patent is liable to pay "reasonable compensation" to the patentee for any damages suffered by the patentee, from the publication date of the patent to the time that it is issued. All application are confidential until they are published eighteen months after filing (section 10(2) of the Act refers).

Publication acts as a form of deemed public notice that rights may exist in the invention. After the patent has issued, a process which may take several years, the person who infringes is liable for any "damages" suffered by the patentee (Section 55(1) refers).

A patent is a form of property which may be sold or licensed. If sold, the buyer becomes the patentee. If licensed, the patent remains the property of the patentee, but the invention can be made used or sold in accordance with the terms of the license. A license allows the licensee to do something which the licensee could not otherwise legally do. There are basically four types of licenses that can be granted in respect of patents: (a) an exclusive license where the licensee alone can make, use or sell the invention; (b) a non-exclusive license which allows the licensor to license third parties; (c) a sole license where the licensor retains the right to practice the invention; and (d) a compulsory license which is a license granted by the Commissioner of Patents without the consent of the patentee.

An invention should be maintained confidential at least until the first application is filed, as public disclosure of the invention can bar the obtaining of patent protection. Although Canada has a one year grace period (section 28.2 refers) allowing disclosure, this grace period is not available in most other jurisdictions. As well, if protection in a foreign country is desired, the foreign application must be filed within twelve months of the Canadian filing date. If this is done, protection in that foreign jurisdiction will be retroactive to the Canadian filing date (so called "priority filing" under the Paris Convention referred to in section 28.1(a)(ii))