This is our top-level category; using another metaphor, it's our root category.

Every other category should be a subcategory of at least one category; and every article should be in at least one category but will often be suitable for two or more.

If two categories have overlapping subject-matter with each having some that's not in the other (eg New Zealand and Tasman Sea or Palmerston North and Manawatu River), they can each include (in the text portion) a link to the other, but neither should be a subcategory of the other. We will use the project:categorisation page for detailed reasons and recommendations, including ways of arranging articles and subcategories in other than strict alphabetical order.