Comparative law notes
Under the common law, a breach of duty - whether prescribed by law or contract - conveys the notion that the person owing the duty did not perform or did not discharge it as prescribed. To the extent that performance was therefore not strictly conforming (i.e., there was a deviation from what was owed), the concept of "breach" is akin to the German concept of Leistungsstörung. However, the concept of a Leistungsstörung is tied to so many different fragmented rules and remedies depending on the type of Leistungsstörung involved and is in fact so rooted in the unique dogmatic structure of the German law of obligations (with its "general part: and its "special part" for contract types), one should stay way from "breach of duty" as a translation for Leistungsstörung, unless the context is very broad and the reasons for and consequences of the breach/non-performance are not discussed. Most of the time, we would therefore recommend a more abstract neologism "duty performance irregularity"
