Notes: This category is to be deleted. Please move the articles to appropriate categories.
These articles are about an abstract concept or likewise, i.e. something which you cannot define as being one particular thing, rather an idea which is manifest in many physicals things in lots of slightly different forms.
This category has the following 2 subcategories, out of 2 total.
Pages in category "Concepts"
The following 21 pages are in this category, out of 21 total.