関係 and 関連: trust, related books and connections studied
Compare a relationship of trust, a question about growth, three related books and a study of sleep and concentration. Read the connection's targets without turning a question or study into proven causation.
Trust between people and a question about phenomena
「二人は仕事を通じて信頼関係を築いた。」 (The two built a relationship of trust through work.)
「気温と植物の成長にはどんな関係がありますか。」 (What relationship exists between temperature and plant growth?) Building trust between two people and asking about temperature and growth have different contexts. The question does not itself supply an answer about that relationship.
Three books related to the question
「質問に関連する資料を三冊借りました。」 (I borrowed three books related to the question.)
関連する connects the books with the question. Three books were borrowed; that fact does not also report a solved question or completed reading.
Studying sleep and concentration
「睡眠と集中力の関連について班で調べています。」 (Our group is studying the relationship between sleep and concentration.)
The group is studying a connection between sleep and concentration. Research in progress is different from a reported proof that one causes the other.
Does studying the 関連 between sleep and concentration mean a cause and effect have been established?
Show the answer and why
No. It reports an ongoing study of their relationship, not proven causation. Likewise, the separate question about temperature and growth does not contain its own answer.