Something that is peripheral is not as important as something else: The book contains a great deal of peripheral detail.
Less important than the thing something is connected with or part of: Try not to be distracted by incidental details.
To me, based on dictionaries, these two words are so close that I hardly can differentiate them from one another.
For instance, I cannot tell the following collocations apart:
- peripheral / incidental problem
- peripheral / incidental information
- peripheral / incidental role
- peripheral / incidental activities
Also, Ngram proves that there are lots of hits for all these combinations including both of the adjectives in my question.
Does it mean that these two words are the same? If not, how do they differ?
Which choice is better with each words: "problem", "activities", "information", "role", "issue" etc?
How shall I diagnose the proper combination?
Please let me know about it.