Category theory MOC

Subcategory

A subcategory 𝖣 of a category 𝖒 is a category containing subclasses of objects and morphisms in 𝖒, i.e. for any 𝑋,π‘Œ βˆˆπ–£ also 𝑋,π‘Œ βˆˆπ–’ and 𝖣(𝑋,π‘Œ) βŠ†π–’(𝑋,π‘Œ). cat It comes with the natural inclusion 1 :𝖣 →𝖒 which is clearly a Faithful functor.

  • A full subcategory 𝖣 is a subcategory of 𝖒 for which the inclusion functor is fully faithful, i.e. 𝖣(𝑋,π‘Œ) =𝖒(𝑋,π‘Œ) for all 𝑋,π‘Œ βˆˆπ–£(𝑋,π‘Œ).
  • A wide subcategory 𝖣 is a subcategory of 𝖒 containing all objects of 𝖒.
  • An essentially wide subcategory 𝖣 is a subcategory containing a skeleton category of 𝖒.

Examples

  • 𝖠𝖻 is a full subcategory of 𝖦𝗋𝗉


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