AbstractThe article raises the problem of clarity of the definition of a defect used in contractual and noncontractual relations in construction. The definitions were considered in the framework of Russian, Swiss, European, and international legislation. The aim of the research was to classify this definition to distribute the burden of liability between the parties of the construction contract. The following methods were applied: analysis of the United Nations Convention on Contracts for the International Sale of Goods and evaluating its compliance with ISO quality management systems standards; analysis of the definition of flawed products in Council Directive 85/374/EEC; method of looking at nearby legislation; and analysis of requirements of international contract forms. Based on the definitions of a defect in different official documents, the authors propose a classification that represents a practical result. The following terms were recommended to use: absolute defect as a violation of mandatory technical or consumer requirements of the object, and relative defect as a noncompliance with contractual requirements but compliance with the requirements for the quality of the object.