How clarity is assessed
 Lack of clarity


An unambiguously, concisely formulated application helps the examiner to understand exactly what the invention is about, so applicants need to make sure that the key parts of their European patent applications are drafted in a clear way.

European Patent Convention
Article 84 EPC: Claims

The claims have a very important function because they define the subject-matter for which the applicant is seeking protection. It’s important to remember, though, that they must also be consistent with the description. This means that the claims and the description must not contradict one other.

Consider this example:

"An electrical apparatus comprising a sizeable display and, connected to the display, means for performing processing, the processing providing an unexpected improvement to the displayability and the perceived quality of the displayed images.”

- Is the minimum size needed for a display to be considered “sizeable” clear? No, there is no standardised size or range of sizes that is generally accepted or described as being “sizeable”.
- Is it clear whether images which have been processed in a certain way will generally be of superior “displayability” or of superior “perceived quality”? No. For example, an image in black and white may be perceived as higher quality by certain people or for certain uses, whereas a close-up cropped image in colour may be perceived as better by others or for other uses.
- If a specific kind of processing was confirmed to improve the displayability and perceived quality of an image, could this improvement generally be considered “expectable”? No, because the term “expectable” is not objective.

More specifically, the claims should: 

Define the matter and extent of protection being sought

Claim: A hair dryer comprising a casing, an air fan, means for air heating, means for determining the temperature of the heated air and means for controlling the air heating means.

Reasoning: The hair dryer and all of its essential parts are defined, meaning that the extent of protection is not ambiguous.

Be clear

Claim: The improvement of a transmission system.

Reasoning: What is meant by an “improvement”? Is it referring to a particular type of software in the engine's controller? Is it an engine gearbox with a particular number of gears, or a new wireless protocol? Is the whole transmission system protected under the scope of the claim?

Be concise

Claim: A domestic heating appliance selected from a microwave device, a toaster, a cooking oven, a sandwich maker, a hair dryer, an electric blanket or a combination thereof, wherein the appliance comprises a screen and/or LED lights and/or an outer enclosure comprising aluminium and/or an outer enclosure comprising a resin coating and/or an anti-sliding support comprising at least two rubber legs.

Reasoning: The claim includes so many alternatives (some of which are not compatible together) that it is impossible to determine the actual extent of the scope of protection, also making it impossible for the public to identify all cases in which the patent can be infringed. 

Be supported by the description

Claim: A carbon fibre cable characterised in that it has a single conducting filament.

Reasoning: The description states that a carbon fibre cable needs many single conducting filaments to solve the technical problem of the invention.



Clarity plays a key role in the evaluation of claims in a patent application as it can have a big impact on the search results.  

But how can we tell if something is clear enough? To ensure a common understanding of sufficient clarity, examiners, applicants and the general public rely on a series of parameters.

The following examples show some of the common pitfalls when drafting claims. 

In general, we recommend:

Using commonly accepted technical terms

Claim: An integrated repair interface. 

Reasoning: “Integrated repair interface” is a vague expression. Does it refer to a robot? A computer program? A screwdriver?

Aligning the claims with established categories

Claim: Connection of a transceiver to a telecommunication network.

Reasoning: The term “connection” is ambiguous as it is not clear whether it refers to a method or an arrangement for connecting the transceiver. As a result, it is not clear whether it belongs to the method claim category or the apparatus claim category.

Clearly distinguishing between the product and apparatus claims and the process and use claims will help to clearly establish the scope of the claim.

Specifying the intended use, which may imply key restrictions

Example: A hook for a crane as opposed to a hook for fishing.

Reasoning: Depending on the purpose, technical specifications can differ greatly. A “hook for a crane” implies that the hook will be subject to certain size and strength requirements that differ from those required for a “hook for fishing”.

On the other hand, we do not recommend using:

Approximate or relative terms 

Example: A very long and thick cable to connect two transmitters.

Reasoning: Relative terms such as thick, thin, wide, strong, light, heavy, large and small result in the scope of protection being unclear, unless they have a pre-assigned, recognised meaning in the particular art. For instance, “near-infrared” and “far-infrared” are technically defined ranges of wavelength in the light spectrum, despite “near” and “far” in themselves being relative terms.

Contradictory, inconsistent or unsupported information

The claims specify a food fryer comprising a perforated metallic steel basket to be immersed in the oil tank but one of the embodiments features a food fryer without a basket.

For a comprehensive list of clarity issues, have a look at section 4 of the 
Guidelines for Examination on clarity and the interpretation of claims.




When an examining division contemplates raising an objection that the application does not meet certain requirements, the burden of proof initially lies with the division. The division must therefore provide detailed reasoning to substantiate its objection (as required by Rule 71(2) EPC).

Generally speaking, when raising an objection of lack of clarity, the examiner must state:  

  • The claim it relates to
  • The terms or expressions in the claim that do not meet the requirements of Article 84 EPC
  • Which requirements of Article 84 EPC are not met, such as clarity, conciseness, definition of scope or support in the description
  • Why these requirements are not met (for example, by referring to the Guidelines for Examination or established case law)
  • If there are multiple interpretations, which one will be used in further communications
  • Possible solutions for overcoming the objection (where appropriate)

Depending on the degree of severity, clarity issues can have different consequences.

  • For minor issues, the patent examiner might suggest correcting these in the search opinion.
  • If claims are partly unclear, but can be reasonably interpreted on the basis of the description, the examiner will carry out a complete search on the basis of the application as a whole and set out the interpretation of the claims used for the patentability analysis in the search opinion.
  • For major clarity issues, the search for prior art documents and/or the search opinion may be restricted. In such cases, the examiner may issue an incomplete search report or – in exceptional cases – a declaration of no search, stating the reason for the restriction and the scope for search and subsequent examination. The search opinion will then indicate that it was not possible to carry out a meaningful examination of all or part of the application. In some cases the examiner may request further clarification in order to perform the search.

To learn more about formulating claims, how this could affect the application and how clarity issues can be resolved, see the course Search reports and written opinions.


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