18Dxx Categories with structure

• 18D05 Double categories, $2$-categories, bicategories, hypercategories
• 18D10 Monoidal categories (= multiplicative categories), See also {19D23}
• 18D15 Closed categories (closed monoidal and Cartesian closed categories, etc.)
• 18D20 Enriched categories (over closed or monoidal categories)
• 18D25 Strong functors, strong adjunctions
• 18D30 Fibered categories
• 18D35 Structured objects in a category (group objects, etc.)
• 18D99 None of the above but in this section