圏の定義,圏の例,isomorphism,free monoid
monomorphism/epimorphism, product, representable functor
duality, coproduct, equalizer/coequalizer
subobject, pullback
limit, colimit
natural transformation, functor category
bifunctor lemma, functor category is CCC
equivalence of categories, Yoneda embedding
Yoneda lemma, Yoneda principle