"Closely connected" or "tightly connected" are both phrases that can be used to describe something that is closely pnked or related. For example, you could say:

"The two departments are closely connected, with many employees working on projects that span both areas."

"The different parts of the system are tightly connected, so it's important to understand how they all work together."

"The two companies have a close connection, with many shared interests and goals."

You could also use the phrase "intimately connected," which means that there is a very strong and close relationship between two things. For example:

"The two countries are intimately connected, with a shared history and many cultural ties."

"The different parts of the organization are intimately connected, so it's important to maintain good communication and cooperation between them."