How to make DB structure in MongoDB?

Question

MongoDB

Good day!
There are groups of "dictionaries", each dictionary has a set of words.
What is the best way to build a database if I need to store and modify data?
What is the best way to do this:
- store groups and dictionaries in different collections and in dictionaries write the ID of the group to which it belongs;
- store both groups and dictionaries and words in one collection in the form: group>arrayFromDictionaries>dictionary>arrayFromWords;
- another variant...