► related/connected adjective used about things that have a connection with each other. Connected is not used before a noun: · Physics and Maths are closely related.· The two problems are connected.· homelessness and other related issues
► linked adjective having a direct connection – often used when one thing is the cause of the other: · Skin cancer is directly linked to sun exposure and damage.· Two closely linked factors produced this result.
► interrelated/interconnected adjective used about two or more things that are connected with each other and affect each other in a complicated series of ways: · The various parts of society are closely interrelated.· The book consists of a series of interconnected essays.
► interdependent used about two or more things, countries, people etc that depend on each other, and cannot exist or continue without each other: · The two countries’ economies have become increasingly interdependent.· interdependent relationships between species· Darwin said that all life on Earth is interdependent.
► relevant adjective related to what is being discussed or to a particular area of activity: · The exam tests the way you select and organize information relevant to the question.· Applicants should have several years’ relevant experience.
► be bound up with something to be very closely connected – used about two things that need to be considered together: · The history of the city has long been bound up with the sea.· Your professional development is closely bound up with personal growth.
depending on or necessary to each other: 
countries with interdependent economies► see thesaurus at related—interdependently adverb