Definitionslinie

Definitionslinie is a German term that translates roughly as “definition line.” It is not a standard, universally used term in formal mathematics, but appears in some German-language teaching texts and reference works. In such contexts it refers loosely to a line that serves to illustrate, delimit, or define a concept, rather than to a rigorously defined mathematical object with a fixed, universal meaning.

In practice, the meaning of Definitionslinie varies by discipline and author. It can denote a line that marks the boundary of a definitional region, a locus of points satisfying a defining condition, or a line presented in an example to accompany a definition. Because the term is not part of the canonical terminology, its exact interpretation should be inferred from the surrounding text. In contemporary German mathematics, more precise terms such as Definitionsbereich (domain of definition), Definitionsmenge (set of definitions), Grenzlinie (boundary line), or Locus are preferred.

Usage outside mathematics is also possible, particularly in pedagogy or semi-formal discussions, where Definitionslinie may describe a conceptual line used to delineate or clarify a definition. As with many historical or instructional labels, readers should rely on context to decide whether the term points to a formal notion or a teaching aid.

See also: Definitionsbereich, Definitionsmenge, Grenzlinie, Locus, Boundary line.