Strategic Claims Across Jurisdictions: Navigating ‘Comprising’ vs ‘Characterised in that’ in US and EP Communication

1) Conceptual contrast and why it exists: US “comprising” vs EP “characterised in that”

At the heart of cross‑jurisdictional patent communication lies a fundamental difference in how claims are framed and justified. In the United States, the transition term “comprising” signals an open, inclusive claim. It asserts that the claimed invention must include the listed elements, but it may also include others not recited. This openness is not a drafting trick; it reflects the US system’s emphasis on providing a scope that captures practical variations and after‑arising implementations, so long as the specification enables the claimed breadth. The legal culture favors avoiding unnecessary self‑limitations and retains a flexible space for continuation practice, where applicants pursue broader or differently focused claims based on disclosed matter.

In the European Patent system, by contrast, the two‑part form “A [known preamble] … characterised in that [novel features] …” (CIT) is a convention deeply embedded in the EPO’s novelty and problem–solution approach. The preamble states the features of the closest prior art, anchoring the claim to a recognized baseline. The characterising clause isolates the distinguishing features that confer novelty and support inventive step. Although two‑part form is not always mandatory, EPO examiners often encourage or require it when there is a clear closest prior art. Its rhetorical and analytical function is to make the contribution over the art explicit and to facilitate the problem–solution reasoning that drives EP examination.

These divergent forms have functional implications. In the US, “comprising” deliberately tolerates additional, unrecited elements in accused products without surrendering claim scope. A competitor cannot escape infringement merely by adding something extra. In Europe, the two‑part form steers everyone—applicant, examiner, and later the opposition division—to think in terms of which claim features truly differentiate the invention from the best prior art and what technical effects these features credibly produce. The EP focus is to prevent both overreach (by requiring support under Article 123(2) EPC) and hindsight (by using the problem–solution framework to evaluate inventive step), rather than to maximize openness in the US sense.

The contrast also reflects differences in statutory and case‑law priorities. US practice is particularly sensitive to written description, enablement, and indefiniteness, but it permits broader framing if supported; EP practice is acutely sensitive to added matter (Art. 123(2) EPC) and clarity (Art. 84 EPC), and scrutinizes whether any asserted technical effect is genuinely and unambiguously derivable from the application as filed. Consequently, US claims are often drafted to avoid needless narrowing, while EP claims are drafted to make the novelty‑conferring features explicit and technically meaningful within the problem–solution method.

2) How the contrast shapes drafting, amendments, and examiner communications

Because US “comprising” claims are open, the drafting strategy is to include enough structure to define the invention but not so much that later‑found alternatives or add‑ons would evade the claim. Writers often prefer “comprising” to “consisting of” (closed) or “consisting essentially of” (partially closed) unless a narrower scope is intentional, for example to avoid prior art or to specify a critical composition. The specification is built to support a family of claims ranging from broad to fallback, anticipating continuation practice and potential restriction requirements. Definitions, optional features, and examples are drafted to enable claim sets that can shift emphasis without adding new matter.

In prosecution, US interviews and responses tend to defend breadth through enablement and to resist importing limitations from examples unless necessary for allowance. Communications emphasize that non‑recited elements do not depart from the invention when the core recited elements are present. Applicants stress that the claim captures the inventive concept even alongside additional features. This stance preserves infringement reach and supports later continuation filings that adjust focus, for instance from apparatus to method claims or from general to more specific embodiments.

In Europe, two‑part claims constrain how you articulate novelty. When amending, you must show that the preamble genuinely corresponds to the closest prior art and that the characterising features are exactly those that distinguish and solve an objective technical problem. Any amendment must be directly and unambiguously derivable from the original disclosure. This is a higher bar than many US practitioners expect; paraphrase or generalization beyond what was originally disclosed can trigger an Art. 123(2) objection. Therefore, EP drafting builds in explicit fallback positions—alternative ranges, parameter definitions, optional steps, and feature combinations—expressly and clearly described to permit surgically precise amendments.

Examiner communications in the EP center on the objective technical problem and the technical effect produced by the distinguishing features. Applicants need to maintain strict communication discipline: any assertion of effect must be credibly supported by the application as filed, not introduced later as a speculative benefit. The structure of argumentation follows the problem–solution steps: identify the closest prior art, define the distinguishing features, state the objective technical problem (without hindsight), and show why the skilled person would not obviously arrive at the claimed solution. Because two‑part form explicitly reveals the distinguishing features, it helps organize these arguments. However, it also anchors the discussion and narrows room for improvisation; unplanned statements in interviews can inadvertently commit the applicant to narrower interpretations or unproven effects.

Another important practical difference is the handling of intermediate generalizations. In the US, applicants can often amend by combining disclosed features as long as the written description supports those combinations. In the EP, combining features from different embodiments or extracting a feature from a specific context may be rejected as an intermediate generalization unless the original filing clearly indicates that the feature or combination is generally applicable. This makes the initial disclosure architecture crucial: it must be written to demonstrate that certain features are independently significant or combinable across embodiments.

3) Alignment techniques for dual US–EP strategies

To harmonize a single application for both jurisdictions, drafting must anticipate the open US style and the EP two‑part logic simultaneously. This starts with a disclosure that is rich, modular, and explicit about technical relationships:

• Provide clear definitions and enumerated alternatives so that “comprising” claims are enabled across variations, while the EP record shows which alternatives matter for the technical effect.
• Write feature groupings at multiple levels: core elements, preferred subsets, optional extras, and parameter ranges. Indicate when a feature is independently beneficial or can be combined with others without dependency. These signals are vital to avoid EP added‑matter traps when creating the characterising portion.
• Document technical effects and their boundaries. If a performance improvement depends on a parameter range or a material choice, state that dependency explicitly and, where possible, include data or reasoned explanations. This supports EP problem–solution arguments and also provides a US narrative for broad claims with narrower, effect‑tied fallbacks.

For template phrasings, align to each forum’s expectations without cross‑contaminating the record:

• US claims: prefer “comprising” for breadth. Use “optionally” and “in some embodiments” to keep optional features from becoming implied requirements. Maintain consistent terminology to avoid indefiniteness challenges while preserving flexibility. In responses, emphasize that non‑recited elements may be present without departing from the scope.
• EP claims: prepare two‑part formulations where feasible. Phrase the preamble to map the closest prior art accurately, avoiding over‑inclusion that collapses novelty, and restrict the characterising clause to the precise distinguishing features that produce the technical effect. In responses, articulate the objective technical problem neutrally and ground every asserted effect in the filed disclosure.

Disclosure structuring should include express fallbacks designed for EP while harmlessly broad for US:

• Enumerated ranges with explicit endpoints and sub‑ranges that can be cleanly extracted during EP amendments without creating undisclosed generalizations, while in the US they preserve broad enablement.
• Alternative materials, configurations, and steps described as independent, combinable, or mutually exclusive, as appropriate, so the EP record shows direct and unambiguous support for each combination used in the characterising clause.
• Dependent claim trees that mirror these alternatives, signaling intended modularity. In the US, these support continuations; in the EP, they provide ready‑made, disclosure‑backed amendments.

For interview and response tactics, apply strict communication discipline:

• Pre‑commit only to technical effects supported by the as‑filed description. Avoid new, unsubstantiated advantages in EP, which risk both credibility and added‑matter objections if you attempt to amend around them.
• Avoid accidental narrowing by refraining from statements that suggest features are essential unless the application clearly says so. In the US, keep optionality explicit to preserve continuation paths; in the EP, avoid language that could be read as disclaiming broader generalizations unless strategically necessary.
• Maintain consistent terminology across submissions. Shifts in phrasing can trigger clarity concerns in EP or claim construction issues in US litigation. Define terms once and reuse them.

Finally, plan for divergence without conflict. A single disclosure can serve both systems if it is drafted to be rich in explicit alternatives and effects. But prosecution paths may differ: the US may maintain broad “comprising” claims while the EP converges on a narrower two‑part claim highlighting a particular technical effect. Ensure that arguments in one jurisdiction do not undermine the other. For example, avoid US statements that imply a feature is always necessary if EP flexibility is still needed, and avoid EP statements that appear to disclaim broader embodiments central to US continuation strategy.

4) Short practice: analyze mini‑scenarios to select jurisdiction‑appropriate phrasing and avoid pitfalls

When you encounter a scenario with a core concept plus performance‑enhancing options, your first decision is whether the core concept is independently inventive over the likely art or whether the enhancement is the true differentiator. If the core is inventive, US “comprising” claims can focus on that concept while keeping enhancements optional. In EP, the two‑part claim would include the core in the characterising clause only if it distinguishes over the closest prior art; otherwise, the enhancement becomes the distinguishing feature. The decision turns on the evidence of technical effect and the specific closest prior art identified.

In cases where competitors might add peripheral elements, the US “comprising” approach ensures that such additions do not carve out non‑infringing safe harbors. Your claim should recite the essential elements that define the inventive nucleus, leaving room for non‑essential add‑ons. By contrast, when shaping the EP two‑part form, confirm that the preamble does not inadvertently include a feature that should sit in the characterising clause. Over‑crowding the preamble can erase novelty, forcing you into narrower amendments with possible added‑matter risk.

If you need to amend to overcome art, US practice allows you to introduce a narrowing feature that was clearly described, often without the risk of “intermediate generalization” being policed as strictly as in EP. However, think ahead: if that narrowing feature was described only in a very specific context, US courts may later construe the claim in light of that context. In EP, the same amendment would face scrutiny under Art. 123(2). To mitigate, the original description should have presented the feature as generally applicable or combinable, not exclusively tied to a particular embodiment.

When arguing inventive step in EP, be cautious with technical effects. If your original filing supports an improvement only within a stated parameter window, do not argue a universal effect across all embodiments. Doing so invites objections and undermines credibility. Instead, tie the effect to the disclosed conditions and, if necessary, adjust the characterising clause to match. In the US, you can still maintain broader claims using “comprising” while placing effect‑conditioned features in dependent claims or continuations.

For communications, train yourself to separate narrative flourish from legal commitment. In EP interviews or written submissions, avoid introducing fresh advantages, speculative mechanisms, or new technical rationales not present in the filing. Keep to the documented effects, and phrase the objective technical problem in a way that neither trivializes the advance nor overstates the contribution. In the US, likewise avoid statements that inadvertently narrow the invention, such as describing an optional feature as required. Maintain “in some embodiments” language and refrain from definitive necessity unless you truly intend to limit the claims.

In summary, the US “comprising” approach and the EP “characterised in that” two‑part claim format embody different philosophies: one aims at inclusive breadth and flexibility; the other insists on explicit differentiation and technically grounded problem–solution reasoning. These differences shape how you draft, amend, and argue. A coordinated strategy—rich, modular disclosures; explicit fallbacks; disciplined communications; and jurisdiction‑tuned claim phrasing—enables you to navigate both systems without sacrificing scope or validity. Mastery lies not only in knowing the labels but in anticipating the operational consequences of each word you choose and each effect you assert.