General description of a Greek αυλη:
An αυλη could refer to a courtyard in front of the house or a courtyard, open to the sky, within the house, around which rooms were located. This courtyard was surrounded on all four sides with colonnades, creating a peristyle. These were used for exercise mainly but occasionally meals were eaten here. The household altar of Zeus was also located in the αυλη.
General description of a Roman atrium:
The Roman atrium was the first main room into which guests entered from the front door. In early Roman houses, the atrium was the only room. As wealth increased, so did the number of rooms, all of which led off the atrium but the atrium remained the most important room. It was open to the sky, allowing rainwater to collect in the impluvium. The household gods, the Lares, were kept here, as were the wax portraits of family ancestors, and the lectus genialis. Its main and most important function was to receive clients and guests. As such, atria could be very elaborate and were an important part of displaying and maintaining status.
Similarities between a Greek αυλη and a Roman atrium:
Open to the sky.
Rooms were located off this centralised space.
Religious icons were kept here.
Differences between a Greek αυλη and a Roman atrium:
The αυλη seems to have always been a courtyard at heart, that is to say, an outdoor area. In contrast, the atrium was always a room (in early houses, the only room).
The αυλη was surrounded on four sides with colonnades creating a peristyle or cloister which was used for exercise. Indeed, Vitruvius appears to use aula and peristylium synonymously (6.7.4). The Dictionary of Greek and Roman Antiquities similarly notes that αυλη was “also used by later writers as equivalent to περιστύλιον”, citing Pollux (who wrote in 2nd cent. AD).
In contrast, Vitruvius distinguishes between peristylium and atrium in the Roman house (6.5.2 – see below). For Vitruvius, therefore, neither αυλη nor aula are the same as atrium. The atrium had columns, no doubt to support the roof, but I have found no evidence that they were employed to create a colonnade nor that the atrium was used for exercise. Rather, the atrium appears to be a much more enclosed space than the αυλη. I’m not sure just how open to the sky each space was. It seems that the αυλη was entirely open while the atrium had an opening, the compluvium, to allow rainwater to run into the impluvium.
The atrium was first and foremost a room for receiving clients/guests. A crowded atrium signified great social and political success (frequens atrium – Seneca, Epistles, 76.12); an empty one, failure (atrium vacuum – Seneca, Epistles, 22.9). I have not come across aula (in Latin) being used in this way, to denote a room in which one’s social status hangs in the balance.
Vitruvius goes so far as to say that those in the lower classes do not need an atrium since they don’t receive clients (but rather are clients) (6.5.1). On the other hand, those of the highest rank have need of lofty atria:
faciunda sunt vestibula regalia, alta atria et peristylia amplissima
Note again Vitruvius’ distinction between atrium and peristylium, the latter of which he sees as synonymous with aula. Later, he clarifies that in the Greek house:
hospites advenientes non in peristylia sed in ea hospitalia
recipiantur / arriving guests are not received in the peristylia but
in the guest accommodation (6.7.4)
Thus, the function of the aula and the atrium are not at all the same. In very early Greek houses, the αυλη was a courtyard you would pass through on your way to the δωμα or μεγαρον, the great hall. This reinforces the idea that the αυλη was not the main reception room in the Greek house (see this diagram of Odysseus' palace).
As Vitruvius wrote:
atriis graeci quia non utuntur, neque aedificiant … / not using atria,
the Greeks do not build like us … (6.7.1)
But how did the Romans use the (Latin) terms aula and atrium?
By far the most common use of aula in Latin is to mean court, as in the sense of a ruler’s entourage and household, or simply a palace.
Nevertheless, the Romans did sometimes use aula to mean a forecourt, usually where animals were kept, for instance a barking dog in Horace (Epistles, 1.2.66) and sheep in Propertius (3.13.39). Thus, this use equates with one Greek sense of the word.
Otherwise, it is hard to be 100% certain that aula was used synonymously with atrium. As noted above, Vitruvius doesn’t use aula and atrium interchangeably as he clearly sees the two terms as describing two quite different spaces, different in form and function.
However, Horace’s use of aula (in Epistles, 1.1.87) is clearly being used as a synonym with atrium. I say this because of the reference to the lectus genialis, the marriage bed which was kept in the atrium (unoccupied!), opposite the front door (lectus).
Another possible synonymous use of aula with atrium is in Juvenal (Satires, 1.5) where he advises someone not to have children lest they divert his attentions from his patron:
nullus tibi parvulus aula luserit Aeneas / don’t have a little Aeneas
playing in the aula
[which is actually a reference to Dido’s lament:
si quis mihi parvulus aula luderet Aeneas /
if in my aula a baby Aeneas were playing (Aeneid, 4:328)]
Juvenal (and Dido) may mean the atrium or the aula proper, a peristyle or they could just as easily mean the forecourt. The problem is that, when translating, you could equally insert hall/atrium/courtyard and still make perfect sense without ever knowing for sure what the original intention was.
Having said that, it seems to me that when it is important to the understanding of the sentence, atrium is used. For example, the biting remarks of Seneca about the gap between appearances and reality relies on the reader understanding that he is talking about the atrium and its function as a marker of status:
non facit nobilem atrium plenum fumosis imaginibus / an atrium full of
busts grimy with smoke do not make a nobleman (Epistles 44.5)
Or again in Juvenal:
tota licet veteres exornent undique cerae atria, nobilitas sola est
atque unica virtus / you may decorate your entire atrium everywhere
with ancient wax portraits but the one and only nobility is excellence
of character (Satires, 8.19).
And in Horace:
cur invidendis postibus et novo sublime ritu moliar atrium? / why
should I go to all the effort to build envy-inducing doorposts and a
towering atrium? (Odes, 3.1.45-46)
I don’t think that in any of these examples the full force of the author’s point would be felt if they had used aula. This is, in my opinion, because the perceived functions of the aula/αυλη and the atrium were different even if over time all three terms came to suggest the form of a central hall-like space. Only the distinctly Roman atrium and its peculiarly Roman function as reception room could be used here.