Maybe "characterization" but I am not sure about that.
The "characterising portion" of a patent claim is a well-founded term, used in claim structure and definition requirements of EPC and is therefore widely understood.
In CZ (as well as for European Patent and in many other European countries) patent claims use the form of the so-called Hartig definition consisting of 2 parts:
- "předvýznaková část" (preamble) defining the state of the art prior to the invention
- "význaková část" - (characterising part/portion) - defining the inventor´s contribution to the art in the concerned technology.
In this system, patent protection is sought for the characterising portion only. This part normally starts with the term "vyznačovaný" or "vyznačující se" - in English "characterized by" or "characterized in that".
The applicant is asked to rephrase the characterising portion of the claim so that it does not contain features (znaky) of a method (way of production) as the invention category is product (i.e. not method).
(You can either apply for a product or a method of production or both but you cannot mix the claims freely in the application.)

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Note added at 55 mins (2009-07-08 09:40:39 GMT)
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I believe "význak" means the whole "význaková část" in your text. This characterising portion (význak - význaková část) may then contain several "features" of the invention, the Czech for which is "znak".