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Uniqueness is an assignment in which a character (for example a word, a sentence) has exactly one meaning .

If there are several meanings, there is ambiguity , if there are exactly two meanings, one speaks of ambiguity and if the meaning is fuzzy, there is uncertainty (language) .

Social situations that cannot or can hardly be misunderstood are also clear - in contrast to conflict situations whose stimulus constellations are ambiguous and whose processing requires greater effort than is the case with unambiguous situations. The creation of really clear situations, however, is a difficult undertaking, since the perception and processing of stimuli by different individuals is usually different from one another and consequently could probably also be assessed as ambiguous. In this respect, it makes sense in a social context to speak of more or less clear-cut situations.


Linguistic expressions are often ambiguous. Scientific work should, however, be as clear as possible.

One of the most difficult problems with automatic natural language processing is resolving the ambiguity of linguistic characters upon interpretation. People can do this easily, as does the distinction between wanted and unwanted ambiguity. Language processing programs of today's generation often fail because of this. The context can make ambiguous texts unambiguous.

There are several ways to create clarity.

By changing the language, the earlier uniqueness of a word can be lost and polysemic or homonymous words with two or more meanings are formed.

In order to make a language clear, it can be standardized. This is especially true of programming languages .

In science it often has advantages to use foreign words whose meaning is not transparent or can be derived from the components. It is then easier to define them precisely and unambiguously, because long-lasting basic meanings of the mother tongue otherwise cover up the definitions. Example: "Activity word" is the German word for " verb ". However, a verb does not necessarily mean an activity, while a verb is not necessarily required to indicate an activity. In “I have something” the verb describes a state or relationship rather than an activity. In “Walking takes a long time”, “walking” denotes an activity, but it is a noun, i.e. a thing word. The word “verb” denotes a grammatical class of words, not an activity. The word "activity word" denotes the same class of words, but appears ambiguous, since one associates an activity with it in everyday language.


denote an abstract math problem. We say be a solution of when is a true statement. means solvable if one exists such that it is true. To define uniqueness, we do not necessarily have to assume the existence of a solution. means unique if any two solutions of the same are found.

In predicate logic , uniqueness can be expressed by:

Assignments ( relations ) can be unambiguous or ambiguous in two directions:

  • Legal Unique assignments called pictures or functions (that is clearly: no element of "left" more than an assigned partner on the ".. Right side", the " right partner" of an element is thus clearly determined; this is conceptually makes sense in two " Pages ”separated, for example in characters and their meanings in the case of a language). A function assigns exactly one element of a target set (a y-value) to each element of a definition set (an x-value) .
  • Left unambiguous (so-called injective ) assignments (no element on the right side has more than one partner on the left side) assign each element of the “right side” to a maximum of one, i.e. clearly a “ left partner”.

Functions or images can also be surjective or bijective .

To stay with the example of a language, the set of characters or words would now correspond to the "left side" and the set of meanings or terms to the "right side". A right-unambiguous language would mean that it would not contain any homonyms ; a left-unambiguous language would contain no synonyms . A left and right unambiguous language would consequently contain neither synonyms nor homonyms and would therefore be maximally unambiguous or bijective (example: controlled vocabulary ).

See also