Talk:Injective object

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

A morphism into ${\displaystyle Q}$ extends to a morphism into ${\displaystyle Q}$? 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)Reply

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)Reply

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

So far it is most convenient to use ${\displaystyle {\mathfrak {C}}}$ to be consistent. --Shiyu Ji (talk) 16:41, 1 September 2018 (UTC)Reply

{{ec} It is a good idea of homogenizing notation. Personally, I oppose to C and ${\displaystyle \mathbf {C} }$, which are widely used for denoting complex numbers. I do not like ${\displaystyle {\mathfrak {C}},}$ 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 ${\displaystyle C}$ (in latex). This would be coherent with most well presented mathematical articles. D.Lazard (talk) 16:52, 1 September 2018 (UTC)Reply