Ammianus Marcellinus in the context of "Nerva"

Philippopolis (Ancient Greek: Φιλιππούπολις, Φιλιππόπολις) is one of the names of the ancient city (amongst which are Thracian Eumolpia/Pulpudeva, Roman Trimontium) situated where Plovdiv is today. The city became one of the largest and most important in the region and was called "the largest and most beautiful of all cities" by Lucian. During most of its recorded history, the city was known by the name Philippopolis (Ancient Greek: Φιλιππούπολις, romanized: Philippoúpolis, lit. 'Philip's city') after Philip II of Macedon. Philippopolis became part of the Roman Empire and capital of the Roman province of Thracia. According to Ammianus Marcellinus, Philippopolis had a population of 100,000 in the Roman period.

Philippopolis was in a fertile region on the banks of the Maritsa River (the ancient Hebrus). The city historically developed on seven syenite hills, some of which are 250 metres (820 feet) high, because of which Plovdiv is often referred to in Bulgaria as "The City of the Seven Hills".

Late Latin is the scholarly name for the form of written Latin of late antiquity. English dictionary definitions of Late Latin date this period from the 3rd to 6th centuries CE, and continuing into the 7th century in the Iberian Peninsula. This somewhat ambiguously defined version of Latin was used between the eras of Classical Latin and Medieval Latin. Scholars do not agree exactly when Classical Latin should end or Medieval Latin should begin.

Being a written language, Late Latin is not the same as Vulgar Latin, or more specifically, the spoken Latin of the post-Imperial period. The latter served as the ancestor of the Romance languages. Although Late Latin reflects an upsurge in the use of Vulgar Latin vocabulary and constructs, it remains largely classical in its overall features, depending on the author who uses it. Some Late Latin writings are more literary and classical, but others are more inclined to the vernacular. As such it is an important source of information about changes in the spoken language, while not being a simple replication of the state of the oral language at the time. Also, Late Latin is not identical to Christian patristic Latin, used in the theological writings of the early Christian fathers. While Christian writings used a subset of Late Latin, pagans, such as Ammianus Marcellinus or Macrobius, also wrote extensively in Late Latin, especially in the early part of the period.

Gian Francesco Poggio Bracciolini (Italian: [dʒaɱ franˈtʃesko ˈpɔddʒo brattʃoˈliːni]; 11 February 1380 – 30 October 1459), usually referred to simply as Poggio Bracciolini, was an Italian scholar and an early Renaissance humanist. He is noted for rediscovering and recovering many classical Latin manuscripts, mostly decaying and forgotten in German, Swiss, and French monastic libraries. His most celebrated finds are De rerum natura, the only surviving work by Lucretius, De architectura by Vitruvius, lost orations by Cicero such as Pro Sexto Roscio, Quintilian's Institutio Oratoria, Statius' Silvae, Ammianus Marcellinus' Res Gestae (Rerum gestarum Libri XXXI), and Silius Italicus's Punica, as well as works by several minor authors such as Frontinus' De aquaeductu, Nonius Marcellus, Probus, Flavius Caper, and Eutyches.

The onager (UK: /ˈɒnədʒə/, /ˈɒnəɡə/; US: /ˈɑːnədʒər/) was a Roman torsion-powered siege engine. It is commonly depicted as a catapult with a bowl, bucket, or sling at the end of its throwing arm. The onager was first mentioned in 353 AD by Ammianus Marcellinus, who described onagers as the same as a scorpion. The onager is often confused with the later mangonel, a "traction trebuchet" that replaced torsion powered siege engines in the 6th century AD.

The Great Conspiracy was a year-long state of war and disorder that occurred near the end of Roman rule in Britain. Fourth-century Roman historian Ammianus Marcellinus describes it as a barbarica conspiratio ('barbarian conspiracy') which took advantage of a depleted military force in the province; many soldiers had marched with Magnentius in his unsuccessful bid to become emperor. Few returned, and supply, pay, and discipline in the following years may have been deficient.

The precise chronology of events remains unclear. Ammianus, although being the author of the most comprehensive and widely-cited surviving sources on the Conspiracy, was living in Antioch during the time that it took place. His account is thus likely to be derived from other sources and exhibits inconsistencies with other known documentation.

Valentinus (fl. mid-4th century, died 369) was a Roman criminal and rebel put down after Count Theodosius's arrival in Britain in AD 369.

Ammianus Marcellinus records that Valentinus was a Pannonian whose brother-in-law Maximinus was close to the emperor Valentinian I. Having committed some serious crime, he was able to have his sentence commuted to exile to Britain, where he resided at the time of the Great Conspiracy. Ammianus does not record that Valentinus took part in that barbarian rising, but does claim that he began planning a new revolt after the arrival of Theodosius. He organized fellow exiles and attempted to bribe local troops to his cause. Discovered, he was given over to Duke Dulcitius for execution, but Ammianus notes that investigation into Valentinus's plot was cursory, lest it produce more unrest in the province.

Barbaricum (from the Greek: Βαρβαρικόν, "foreign", "barbarian") is a geographical name used by historical and archaeological experts to refer to the vast area of barbarian-occupied territory that lay, in Roman times, beyond the frontiers or limes of the Roman Empire in North, Central and South Eastern Europe, the "lands lying beyond Roman administrative control but nonetheless a part of the Roman world". During the Late Antiquity, it was the Latin name for those tribal territories not occupied by Rome that lay beyond the Rhine and the Danube (but not for Persia): Ammianus Marcellinus used it, as did Eutropius. The earliest recorded mention appears to date to the early 3rd century.

In research literature, the terms 'Germania', actually Magna Germania, and 'Barbaricum' are sometimes used interchangeably, but they are not entirely identical in the chronological or the geographical senses. The extra-Roman area described as Barbaricum was, from the beginning of the Migration Period, not exclusively inhabited by Germani, even though they represented the majority of the population until the time of Late Antiquity. In the Migration Period, Alans and Huns also pushed forward into this area before and, later (from the 6th century), Slavic tribes populated the area east of the Albis (River Elbe) that the Germani had largely abandoned.

The Juthungi (Ancient Greek: Ιούθουγγοι, Latin: Iuthungicode: lat promoted to code: la ) were a Germanic tribe in the region north of the rivers Danube and Altmühl in what is now the modern German state of Bavaria.

The tribe was mentioned by a few Roman historians, including Publius Herennius Dexippus and Ammianus Marcellinus, stretching from the 3rd to the 5th century CE.

The Castle of Oblivion (Old Armenian: բերդ Անուշ berd Anush), also known as the Prison of Oblivion or the Fortress of Oblivion, was a castle and political prison of the Sasanian Empire located in Khuzestan in southwestern Iran. According to the Buzandaran Patmutʻiwnkʻ and Procopius' Persian War, the name referred to the fact that it was forbidden to mention the name of the castle or its prisoners. It may be identifiable with the fortress of Agabana mentioned by Ammianus Marcellinus as the place of Arshak II's imprisonment. According to Claudia Ciancaglini and Giusto Traina, the Armenian form berd Anush is a borrowing from an unattested Middle Persian name which may be reconstructed as *anōš bard. The form Anyush is a later reinterpretation or Armenianization of the original word, identifying it with the common word anyush 'forgotten'. Ciancaglini argues that the original meaning of the name was not 'Castle of Oblivion'—a sense derived from the Armenian etymological reinterpretation—but rather 'immortal, imperishable fortress' (from Middle Persian anōš⁠ 'immortal').