Supererogatory
Etymology
From Latin "supererogare" (to pay out beyond what is owed), built from "super-" (beyond) and "erogare" (to pay out). It entered moral vocabulary via the Vulgate’s parable of the Good Samaritan, who spends "whatever more" is needed, and now marks acts that exceed duty.
adjective · /soo-per-uh-ROG-uh-tor-ee/
Describing a good deed that goes beyond what duty strictly requires, so that failing to do it would not be wrong.
What it names
A handle for the moral space between the merely permissible and the obligatory — reach for it to praise heroism or generosity without implying everyone was required to match it.
Example
Donating a kidney to a stranger is supererogatory — admirable, but no one can be faulted for not doing it.
Related idea
The opposite of obligatory; supererogatory acts sit in the surplus above duty, whereas obligatory ones are the floor below which conduct becomes blameworthy.