The context sentences for the vocabulary stated in the title all pertain to either death or mortality in the sense of death rates. But what about when discussing the concept of mortality in the philosophical sense. It seems that using 死亡could get confusing.
I suspect that death as a philosophical concept would simply be 死（し）. Do you have any examples in mind of contexts in which it might be confusing? It might be possible to find some translations of foreign philosophers (or writings of Japanese ones) online to see how death is actually discussed.
How would you translate: “I think of my mortality regularly”?
That’s pretty much why I feel it might get confusing. I wouldn’t want to translate back to English and land up with: “I think of my death regularly”.
I’m not so sure about that. According to Jisho.org, 死亡率 means death/mortality rate whereas 死亡 is simply death or mortality.
That’s probably the majority of the usage I’ve seen as well.
As far as word choice, it’s a little bit impersonal so you’ll notice that a lot of the example sentences on Jisho are rather objective and that they all refer to it in a concrete sense:
In addition, I found this which suggests that particular word is used in Japan’s Civil Code and other laws so it may be relegated to official usage only:
I think like @Jonapedia said, 死 or some other way of phrasing it would be used for mortality as a concept.
As @Jonapedia san said, it would be 死 when talking about philosophical stuff. Here’s an example from Jisho.
I doubt they are talking in the literal sense.
I suspect it’s something else entirely because I wouldn’t use 死 to discuss it in Mandarin either. I would probably use something that referred to the limits on life or its finiteness. Hang on…
EDIT: @VegasVed Yeah, I think what I would say is something like ‘I think of the fact that I can’t escape death’ or ‘I think about the fact that all must one day die’. ‘Among human beings, none does not die. I ponder this often.’ That’s roughly what it would sound like if I said it in formal/classical-ish Chinese. I guess you could go with「私も死から逃げられないということをよく考えています。」 I’m not sure how I would make it sound properly philosophical in Japanese.「この世（よ）には不死（ふし）の者（もの）はいない」(‘there are no immortals in this world’), perhaps?