1. Basilica - in Roman architecture, an oblong building with double colonnades inside and a semicircular apse at the end, used for public administration. Many basilicas were converted into Christian churches and thus the term came to be applied to churches

2. Atrium - in Roman domestic architecture, an inner court open to the sky and surrounded by the roof; In Early Christian and medieval architecture, an open court in front of a church

3. Aisle - part of a church, parallel to, and divided by piers or columns - or in rare cases by a screen wall - from the nave, choir, or transept.

4. Colonnade - a line of columns; in Early Christian architecture the columns  separate the aisles and the nave

5. Nave - the central part of the church, flanked by aisles

6. Stylobate - the stepped platform on which colonnades of temple columns are placed, it is actually the floor of the temple

7. Piscina - a stone basin usually placed in the baptistery for baptizing 

8. Kantharos - a type of vessel characterized by its high swung handles which extend above the lip of the pot; in Early Christianity the vessel was used for baptising, symbolising the baptism of Jesus Christ; Christian baptism from the 3rd century onwards indicates that the normal form was to have the candidate stand in water while water from the kantharos was poured over the upper body. 

9. Niche - an apse that has been reduced in size, retaining the half-dome heading usual for an apse

10. Narthex - the antechamber to the nave, from which it is separated by columns, rails, or a wall; used by penitents, candidates for baptism and catechumens 

11. Apse - a semi-circular or polygonal termination of the main building at the liturgical east end (where the altar is), regardless of the shape of the roof, which may be flat, sloping, domed, or hemispherical 

12. Crypt - a stone chamber or vault beneath the floor of a church usually used as a chapel or burial vault possibly containing sarcophagi, coffins or relics; crypts were typically found below the main apse of a church, but that is not always the case

13. Baldachin - a canopy of state over an altar or throne. It had its beginnings as a cloth canopy, but in other cases it is a sturdy, permanent architectural feature, particularly over high altars in cathedrals14. Martyrium - an early Christian mausoleum for a martyr

15. Fortification wall - a fortification used to defend a city or settlement from potential aggressors; in ancient to modern times, they were used to enclose settlements
16. Arch - a semicircular structure that spans a space while supporting weight (e.g. a doorway in a stone wall)

17. Proteichisma - an independent structure opposite and parallel to the main fortification wall, designed to prevent the onslaught of enemies, and in particular to prevent their siege machines to reach the defensive wall

18. Hypocaust - a system of central heating connected with a series of small chambers and flues of tiles or other masonry through which the heat of a fire was distributed to rooms above; used for heating public baths and private houses; the word literally means "heat from below"

19. Forum - a central open space usually surrounded by public buildings and colonnades; it was a gathering place of great social significance, it was often the scene of diverse activities, including political discussions, meetings, etc.

20. Opus sectile - an art technique popularized in Rome where materials were cut and inlaid into walls and floors to make a picture or pattern; the materials (mostly marble) were cut to thin places, polished, and then cut further according to the design

21. In situ - refers to an artifact that has not been moved from its original place of deposition; an artifact being in situ is critical to the interpretation of that artifact and, consequently, to the culture which formed it

22. Necropolis - a large cemetery or burial ground

23. Bishop (episcope) - an ordained or consecrated member of the Christian clergy who is generally entrusted with a position of authority and oversight. All the centres of Christianity were headed by bishops.

24. Ecumenical council - a conference of the bishops of the whole Christian Church convened to discuss and settle matters of Church doctrine and practice.

25. Fresco - any of several related painting types, done on plaster on walls or ceilings. It consists of painting in pigment mixed with water on a thin layer of wet, fresh, lime mortar or plaster. 

26. Arcosolium - an architectural term applied to an arched recess used as a burial place in a catacomb. The word comes from from Latin, arcus - "arch", and solium - "a sarcophagus". Arcosolium is sometimes used incorrectly as meaning 'sarcophagus' but it is really a particular kind of tomb. In an arcosolium the sarcophagus is placed in a recess in the wall of the catacomb and covered by a slab of stone. An arched recess is then hollowed out above this. Many arcosolia are highly ornamented.

27. Portico - a porch leading to the entrance of a building, or extended as a colonnade, with a roof structure over a walkway, supported by columns or enclosed by walls.
28. Triclinium - a formal dining room in a Roman building. The word is adopted from the Greek τρικλίνιον, triklinion, from τρι-, tri-, "three", and κλίνη, klinē, "couch". It was characterized by three couches, the klinai, on three sides of a low square table, those surfaces sloped away from the table at about 10 degrees. Diners would recline on these surfaces in a semi-recumbent position. The fourth side of the table was left free, presumably to allow service to the table.

29. Apodyterium - the primary entry in the public baths, composed of a large changing room with cubicles or shelves where citizens could store clothing and other belongings while bathing.

30. Frigidarium - a large cold pool to drop into after enjoying a hot Roman bath. 

31. Caldarium - (also called a calidarium, cella caldaria or cella coctilium) was a room with a hot plunge bath, used in a Roman bath complex. This was a very hot and steamy room heated by a hypocaust, an under-floor heating system. This was the hottest room in the regular sequence of bathing rooms; after the caldarium, bathers would progress back through the tepidarium to the frigidarium. In the caldarium, there would be a bath (alveus, piscina calida or solium) of hot water sunk into the floor and there was sometimes even a laconicum - a hot, dry area for inducing sweating.
32. Tepidarium - was the warm (tepidus) bathroom of the Roman baths heated by a hypocaust or under-floor heating system. The specialty of a tepidarium is the pleasant feeling of constant radiant heat which directly affects the human body from the walls and floor.

33. Tombstone (Stela) - stone slabs taller than they are wide upon which they are inscribed with simple commemorative epitaphs. This may simply include a bordered written inscription, or one with added iconography of the deceased.

34. Catechumen - one receiving instruction from a catechist in the principles of the Christian religion with a view to baptism.

35. Reliquary - a container for relics. These may be the physical remains of saints, such as bones, pieces of clothing, or some object associated with saints or other religious figures. Often found in crypts.

36. Menorah - a seven-branched candelabrum which has been a symbol of Judaism for almost 3000 years and is the emblem of Israel. It is said to symbolize the burning bush as seen by Moses on Mount Horeb.

37. Venatio (pl. venationes) - a form of entertainment in Roman amphitheaters involving the hunting and slaying of wild animals. Exotic wild beasts from the far reaches of the Roman Empire were brought to Rome and hunts were held in the morning prior to the afternoon main event of gladiatorial duels. Special precautions were taken to prevent the animals from escaping these venues, such as the erection of barriers and the digging of ditches.

38. Hypogeum (or Hypogaeum) - literally means "underground", from Greek hypo (under) and gaia (earth). It usually refers to an underground, pre-Christian temple or a tomb. 

39. Scaenae - the elaborately decorated background of a Roman theatre stage. This area usually has several entrances to the stage including a grand central entrance. The scaenae frons is two or sometime three stories in height and was central to the theater's visual impact for this was what is seen by a Roman audience at all times.

40. Pythos - a storage vessel of large proportions, burrowed in the ground with only the upper part of the vessel being visible. The amount of pythoi in a family determined how rich the family was. It was used for storage of grains and food.

41. Peristyle - a columned porch or open colonnade in a building surrounding a court that may contain an internal garden.

42. Cist (graves) - a stone-built coffin-like box or ossuary used to hold the bodies of the dead.

43. Stucco - a material made of an aggregate, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as a coating for walls and ceilings and for decoration. It was used for covering less visually appealing construction materials, and as a decoration. 

44. Pilaster - a slightly-projecting column built into or applied to the face of a wall. Most commonly flattened or rectangular in form, pilasters can also take a half-round form or the shape of any type of column.

45. Spolia - a modern art-historical term used to describe the re-use of earlier building material or decorative sculpture on new monuments. The practice was common in late antiquity.