A ↑requirement that pertains to a quality concern that is not covered by ↑functional requirements.
The CPRE Glossary
The basis for successful RE is a common understanding of the terms used. The CPRE Glossary covers the core terms of Requirements Engineering—it is the central reference work across all CPRE modules and levels!
The glossaries are also available in various languages for download.
The CPRE Glossary: An overview of the most important Requirements Engineering terms
Please note that the definitions of terms in the glossaries are deliberately in English only in order to exclude any ambiguities or scope for interpretation that may result from translations.