• concept in a terminological system (synonym 1)
• agreed meaning of a term (synonym 2)

Definition: meaning of a term as agreed upon by a group of responsible persons.

• This is related to the definition in the current ISO 1087-1 from the year 2000: "unit of knowledge created by a unique combination of characteristics".
  However, there are good reasons to prefer "meaning" to "unit of knowledge", since the latter is marred by several problems and ambiguities. Thus, there can be agreed meanings for terms like "unicorn", but such meanings do not correspond to any unit of knowledge, since there are no corresponding entities in reality about which knowledge could be gained. We also prefer "meaning" to "unit of thought", in order to avoid the psychological connotations of the latter. We postpone to a later communication discussion of the term "characteristic", which is subject to the same sorts of problems as have affected the term "concept".
• The fact that an identified group of responsible persons (the persons responsible for a given terminological system) share a common understanding of the meaning of a term – typically captured by means of a definition – is important for many of the contexts where the term "concept" is used today in modern informatics. This is what distinguishes concepts, as we propose here understand them, from individual ideas in the minds of cognitive subjects. In particular, the existence of agreed meanings on the part of responsible persons is clearly important for the development of formalized standards, including international standards, but it is important also for other groups responsible for a single terminology.
• Experts often differ as to what is meant by "meaning", sometimes it is expressed as: that which remains constant when a word in one language is translated correctly into another language. More operational interpretations of "meaning" in this context include: Given cognitive subjects demonstrate that they have command of the same meaning of a term when they share the ability, upon receiving information containing this term, to associate it with exactly the same referents. Meaning in this sense is closely related to, but importantly distinct from, definition. Thus the term "concept", on the reading "agreed meaning of a term", does not refer to a corresponding definition, or to any other specific representation of this meaning in some natural or artificial language or in some formal model. One and the same concept (in the sense of "agreed meaning") will typically correspond to several alternative ways of expressing this meaning, and thus to different linguistic expressions in the same as well as in different languages.
• Meanings must in this context be specified, and there are two possible ways to do this in a terminological system: by the linguistic representation of a definition or elucidation, or by a translation of the corresponding general term into a different language, where in the specific context of the terminological system in question the provision of alternative terms is able to convey a sufficient understanding of the meaning in question. Usually the representation of a definition in the form of a statement of necessary and sufficient conditions is preferable. However, sometimes we can only use ostensive definitions. For instance, SARS = that syndrome which a certain defined set of individual patient cases have in common. (Note the way in which an ostensive definition of this sort points to a type or universal in reality, i.e. to a certain multiply exemplified entity.)