重叠 (重疊) chóng​dié
overlap verb
to lie over or cover part of something else; to superimpose or telescope

Due to a design error, the contents of these two drawings overlap.

redundancy verb
unnecessary repetition or duplication of content, functions, or roles

There is a lot of overlap between the functions of these two departments.

reduplication verb
a grammatical process in which a word or part of a word is repeated

There are many verbs in Chinese that can be reduplicated.