General, sir, lord, master...

I was wondering how ancient Romans would have addressed people depending on their social status or their rank in the legion. I know that 'Domine' (vocative form of dominus) can mean master (of a slave), lord or sir. But is there any other word that would convey the nuance between the various English appellations? How would a noble patrician be called by say an plebeian eques? 

How would legionaries call their officers? Would it be domine equally for a centurion, a tribune, a legate or the army's general? Or would they call them by their title only?

There isn't much evidence for military protocol in the Roman legions. Legionaries weren't called 'soldiers' before Augustus (they were referred to as 'Brothers'). Specific ranks would be a little tedious so broad categories are likely, Centurion, Tribune, Legate. What you will have to become aware of is that the Romans may well have not used analogous behaviour to modern armies (a typical Hollywood or literary ploy).

Saluting has been debated for a lo/ng time and most people feel comfortable with a modernesque protocol, but the sources do not mention saluting outside of honouring a commander as opposed to recognising his superior rank as we do. What this means is that ordinary salutes may not have happened, but that soldiers who approved of their commanders may have deliberately or spontaneously saluted them as something.

Incidentially using the word 'Domine' might well have been seen as 'licking the backside'. In fact, such language does exist in letters recovered from Vindolanda. It does not refer to rank, but names the recipient as 'Master'. That's a very subordinate form of phrasing because it infers that you are indentured to the recipient in some way. Legionaries swore an oath of obedience - this was necessary because obedience to another man is the same as slavery, and Roman soldiers would not tolerate such associations. They were free citizens, soldiers or not.

The upshot of this is that I am thinking in  terms of names being more contextual than actual rank titles in many cases. Remember that in the legions, loyalty is fixed toward individuals rather than offices.

Excellent reply by Caldrail.

When a levy of the troops was called, those inscripted swoar an oath (ius urandi) that apparently was taken with more sollemnity than we would have today...after all, the gods themselves were being invoked.

There was also a big difference between the army of the republican days and that of the empire.

I agree that our impressions of the Roman army are more  influenced by Holywood than by the historical record. I don't recall Caesar in The Commentaires mentioning anything other than Primus Pilus, tribunus and Legatus.

Imperator was a titled bestowed on a victorious leader (dux) by his troops, then later ratified by the Senate. 

Whether more fantasy or not, you may find this interesting-- The movie Imperator flimed in Latin & Teutonic (English subtitles)  

Whether fantasy or not, you may find this interesting