static Map<S, Set<S>> ai_wordCategoriesWithElements() {
  final Map<S, Set<S>> wordCategories = ciMap();
  for (S cat : mL("All " + ai_language() + " word categories"))
    wordCategories.put(cat, combinedMechSetsCI(ai_mechListNamesForAngleBracketCategory(cat)));
  ret wordCategories;
}