親睦 and 交流: friendship as an aim and exchange as an activity
Compare lunches and festivals intended for 親睦 with students interacting and a river supporting 交流. Separate an event's aim, actual interaction, and the conditions supporting exchange.
親睦: an aim of closer relations
親睦 (しんぼく) focuses on friendly relations. 「部署間の親睦を深めるため、昼食会を開いた。」 means “We held a lunch to foster friendship between departments.” 親睦を深めるため states the lunch's aim. The action reported is holding the lunch, rather than proving that everyone became close.
「住民の親睦を目的とした小さな祭りがある。」 means “There is a small festival intended to promote fellowship among residents.” 目的とした again identifies an intended purpose. The existence of a festival with that aim does not establish that all residents have already developed close relationships.
交流: interaction and support for exchange
交流 (こうりゅう) describes interaction or exchange between people or groups. 「地域の学生と留学生が料理を通じて交流した。」 means “Local and international students interacted through cooking.” Cooking is the activity through which the interaction occurred, and 交流した reports that they interacted.
「川が二つの町の交流を支えてきた。」 means “The river has supported exchange between the two towns.” The towns are the sides involved in the exchange, and the river is presented as supporting it. The sentence does not make the river a person forming friendships or specify a particular transport method.
Distinguish purpose, interaction, and its support
The 親睦 sentences make the purpose of closer relations explicit. The students' 交流した instead directly states an interaction that occurred. Holding an event for friendship, interacting during an activity, and becoming close are related ideas, but they should not be collapsed into a single stated result.
The river example introduces another focus: what has supported exchange between the towns. That supporting role differs from the students' cooking activity. When comparing 親睦 and 交流, identify whether the sentence presents a relationship as an aim, describes people's interaction, or names something that supports it.
Does holding a lunch 「親睦を深めるため」 prove that everyone from the departments became close?
Show the answer and why
No. The sentence states the aim of friendship and the action of holding a lunch. It does not state that every participant developed a close relationship.