The vocabulary of ancient Roman religion was highly specialized. Its study affords important information about the religion, traditions and beliefs of the ancient Romans. This legacy is conspicuous in European cultural history in its influence on later juridical and religious vocabulary in Europe, particularly of the Christian Church. This glossary provides explanations of concepts as they were expressed in Latin pertaining to religious practices and beliefs, with links to articles on major topics such as priesthoods, forms of divination, and rituals.

For theonyms, or the names and epithets of gods, see List of Roman deities. For public religious holidays, see Roman festivals. For temples see the List of Ancient Roman temples. Individual landmarks of religious topography in ancient Rome are not included in this list; see Roman temple.

The verb abominari ("to avert an omen", from ab-, "away, off," and ominari, "to pronounce on an omen") was a term of augury for an action that rejects or averts an unfavourable omen indicated by a signum, "sign". The noun is abominatio, from which English "abomination" derives. At the taking of formally solicited auspices (auspicia impetrativa), the observer was required to acknowledge any potentially bad sign occurring within the templum he was observing, regardless of the interpretation. He might, however, take certain actions in order to ignore the signa, including avoiding the sight of them, and interpreting them as favourable. The latter tactic required promptness, wit and skill based on discipline and learning. Thus the omen had no validity apart from the observation of it.

The aedes was the dwelling place of a god. It was thus a structure that housed the deity's image, distinguished from the templum or sacred district. Aedes is one of several Latin words that can be translated as "shrine" or "temple"; see also delubrum and fanum. For instance, the Temple of Vesta, as it is called in English, was in Latin an aedes. See also the diminutive aedicula, a small shrine.

In his work On Architecture, Vitruvius always uses the word templum in the technical sense of a space defined through augury, with aedes the usual word for the building itself. The design of a deity's aedes, he writes, should be appropriate to the characteristics of the deity. For a celestial deity such as Jupiter, Coelus, Sol or Luna, the building should be open to the sky; an aedes for a god embodying virtus (valour), such as Minerva, Mars, or Hercules, should be Doric and without frills; the Corinthian order is suited for goddesses such as Venus, Flora, Proserpina and the Lymphae; and the Ionic is a middle ground between the two for Juno, Diana, and Father Liber. Thus in theory, though not always in practice, architectural aesthetics had a theological dimension.

The word aedilis (aedile), a public official, is related by etymology; among the duties of the aediles was the overseeing of public works, including the building and maintenance of temples. The temple (aedes) of Flora, for instance, was built in 241 BC by two aediles acting on Sibylline oracles. The plebeian aediles had their headquarters at the aedes of Ceres.

In religious usage, ager (territory, country, land, region) was terrestrial space defined for the purposes of augury in relation to auspicia. There were five kinds of ager: Romanus, Gabinus, peregrinus, hosticus and incertus. The ager Romanus originally included the urban space outside the pomerium and the surrounding countryside. According to Varro, the ager Gabinus pertained to the special circumstances of the oppidum of Gabii, which was the first to sign a sacred treaty (pax) with Rome. The ager peregrinus was other territory that had been brought under treaty (pacatus). Ager hosticus meant foreign territory; incertus, "uncertain" or "undetermined," that is, not falling into one of the four defined categories. The powers and actions of magistrates were based on and constrained by the nature of the ager on which they stood, and ager in more general usage meant a territory as defined legally or politically. The ager Romanus could not be extended outside Italy (terra Italia).

The focal point of sacrifice was the altar (ara, plural arae). Most altars throughout the city of Rome and in the countryside would have been simple, open-air structures; they may have been located within a sacred precinct (templum), but often without an aedes housing a cult image. An altar that received food offerings might also be called a mensa, "table."