This is the 987th most frequent Chinese word.
密
Dense; close; secret.
In this sentence, '密' is used as part of the word '密切' which means 'close' or 'intimate', describing a close relationship.
這是我最密切的朋友。
This is my closest friend.
Here, '密' is used in the context of '保密', which means 'to keep confidential', indicating the secrecy of information.
請將這些信息保密。
Please keep this information confidential.
In this context, '密' is part of '茂密', which refers to 'dense' or 'thick', describing the density of a forest.