Longman Dictionary of Contemporary English - closely

~ adv 1 if you look at or study something closely, you look at it etc hard, trying to notice everything about it  (watch sb closely)  (The detective was watching him closely, waiting for a reply.) 2 if two things are closely connected or related, there is a strong connection between them or they are very much like each other  (These two subjects were closely linked, and it makes sense to consider them together. | closely resembles)  (Their dialect closely resembles that of the northern provinces.) 3 in a way that makes things close together  (a flash of lightning, closely followed by thunder | We were so closely packed in the elevator, I could hardly move.)