noun
relatedness; relevance; relationship
Abstract noun expressing the degree or state of being connected, relevant, or associated. Often used in formal or analytical contexts.
この二つの事件の関連性を調べている。
We are investigating the relationship between these two incidents.
データの関連
If the relevance of the data is low, the analysis results become unreliable.
関係 is a broader term for 'relationship' or 'connection' between people or things, whereas 関連性 is more formal and often used for logical or statistical connections.
Compound of 関連 (relation) + 性 (-ness, -ity). The suffix 性 is productive for forming abstract nouns expressing a quality or property.