5th Edition is deliberately vague about aging so as to avoid RAW pitfalls but in certain areas such as Timeless Body there seems to be an inherent contradiction: Monks cease to age and no longer require food or drink.
Now I've read that WotC considers this to be: "a "Ribbon", i.e. a neat ability with mostly story, rather than mechanical, applications.
Aside from the 8th level spell Clone there aren't many ways to be effectively immortal, but it seems like Timeless Body would provide it--except for the inherent contradiction of Monks no longer aging and not suffering from the debilities of aging--until they die of old age?!?!?