Talk:Injective object

A strange formulation
I quote: "In other words, $$Q$$ is injective iff any $$\mathcal{H}$$-morphism into $$Q$$ extends (via composition on the left) to a morphism into $$Q$$."

A morphism into $$Q$$ extends to a morphism into $$Q$$? Can someone formulate this more clearly? I cannot, since I am in the process of learning category theory myself, so I do not know what the correct formulation is.78.143.70.6 (talk) 17:40, 27 August 2015 (UTC)


 * The wording may be a bit unfortunate (it's correct though). I have added a diagram, from the corresponding better-written German article, which should help. -- Taku (talk) 21:52, 27 August 2015 (UTC)

Inconsistent notation for the category C
We have at least 3 symbols to denote a category: C, $$\mathfrak{C}$$, $$\mathbf{C}$$. Does it make sense to use one of them consistently? --Shiyu Ji (talk) 16:29, 1 September 2018 (UTC)

So far it is most convenient to use $$\mathfrak{C}$$ to be consistent. --Shiyu Ji (talk) 16:41, 1 September 2018 (UTC)
 * {{ec} It is a good idea of homogenizing notation. Personally, I oppose to C and $$\mathbf{C}$$, which are widely used for denoting complex numbers. I do not like $$\mathfrak{C},$$ which may a source of confusion for a user who has never encountered this font. Thus, I suggest to use $C$ (for isolated occurrences), $C$ (inside html formulas) and $$C$$ (in latex). This would be coherent with most well presented mathematical articles. D.Lazard (talk) 16:52, 1 September 2018 (UTC)