na-adjective, noun
close; closely connected; intimate
Used mainly for a close relationship, connection, relevance, or interaction between people, organizations, ideas, causes, and effects. Often appears as 密接な or 密接に.
両国は密接な関係にある。
The two countries have a close relationship.
健康は食生
Health is closely related to diet.
noun, noun or participle which takes 'suru', intransitive verb
being close together; being adjacent; being in close proximity
Physical closeness or adjacency, especially when things are close together or almost touching. This use is less common than the abstract relationship sense; 隣接 or 接近 may be more ordinary for simple adjacency.
この地区では家々が密接して建っている。
In this district, the houses stand very close together.