Res publica
Res publica is a Latin phrase, loosely meaning ‘public affair’. It is the root of the word ‘republic’, and the word ‘commonwealth’ has traditionally been used as a synonym for it; however translations vary widely according to the context. ‘Res’ is a nominative singular Latin noun for a substantive or concrete thing – as opposed to ‘spes’, which means something unreal or ethereal – and ‘publica’ is an attributive adjective meaning ‘of and/or pertaining to the state or the public’. Hence a literal translation is, ‘the public thing/affair’.
In Ancient Rome
Public property
Res publica usually is something held in common by many people. For instance a park or garden in the city of Rome could either be ‘private property’ (res privata), or managed by the state, in which case it would be part of the res publica.
The state or commonwealth
Taking everything together that is of public interest leads to the connotation that the ‘res publica’ in general equals ‘the state’. For Romans this equalled of course also the Roman Empire, and all its interests, so Res Publica could as well refer to the Roman Empire as a whole (regardless of whether it was governed as a republic or under imperial reign). In this context scholars suggest commonwealth as a more accurate and neutral translation of the term, while neither implying republican nor imperial connotations, just a reference to the state as a whole. But even translating res publica as ‘republic’ when it clearly refers to the Roman Empire under Imperial reign occurs (see quotes below).
