na-adjective, noun which may take the genitive case particle 'no', noun
Describes something that is not multiple, composite, or divided; often used in technical or formal contexts for 'single' or 'unitary'.
この制度は単一の基準で運用されている。
This system is operated under a single standard.
単一の原因で説明するのは難しい。
It is difficult to explain with a single cause.