This glossary lists essential bath-related terminology including both modern vocabulary and Latin and Greek terms. It is based on the glossary found in Maréchal 2020 and Yegül 1992. Greek terminology is transcribed in Latin for reasons of convenience, the original Greek spelling being added in between brackets. Frequently used plural forms are also given for a select number of words. Bath-related terminology is mainly the result of modern scholarship that standardised existing Latin and Greek terms. In the ancient texts, the significance of terms could vary according to the author, the geographical or the chronological contexts of the document (see Rebuffat 1991, 7; Nielsen 1993). Several scholars have already compiled extant glossaries with detailed explanations, including references to ancient authors and inscriptions (e.g. Yegül 1992; Nielsen 1993). For the terminology on bath attendants and staff, see Wissemann 1984. For the terminology of baths and bathing habits in the East, including in the Islamic period, see the glossary by Denizeau and Redon 2009. On Roman architecture in general, see Ward-Perkins 1994 and Ginouvès 1998.

Contributors: SM, KB, AK, CH

Bibliography: Denizeau and Redon 2009; Fagan 1999, 368–372; Ginouvès and Martin 1998, vol. III, 100–110, pl. 53–57; Maréchal 2020, 456–460; Nielsen 1993, vol. I, 153–166; Rebuffat 1991; Ward-Perkins 1994, 491–497; Wissemann 1984; Yegül 1992, 487–494. Detailed references on the Zotero shared library.

To quote this glossary: BATH Network (2024), Glossary of ancient baths, Consulted on INSERT DATE, <https://ancientbaths.com/glossary/>

Alousia (ἀλουσία)	A term literally designating the state of being unwashed. In the ascetic movement of early Christianity, the refusal to bathe was considered a virtue, as it avoided the confrontation with nudity and underlined the sacrament of baptism as the only necessary washing.
Alveus (pl. alvei)	A hot-water pool, mainly found in the heated rooms of Roman-style baths. Most of these pools could accommodate several people at a time. The hot water was supplied by a boiler in the service rooms, mounted above the furnace of the hypocaust. It was kept warm by means of the hypocaust running under the pool and/or by means of a testudo. Alternatively, the alveus was heated only by an underlying furnace or by the hypocaust and wall heating.
Ambulacrum	Monumental corridor in large thermae, mainly found in the baths of North Africa or Asia Minor. These large halls, straight, U- or H-shaped in plan, often had several niches to lodge statues. Besides being used for walks (ambulatio), these could have served a wide variety of functions (meetings, physical exercise, etc.).
Apodyterium	The changing room of a Roman-style bathhouse. These were often equipped with benches, sometimes made out of brick or stone, but most often in wood. Especially in early bathhouses, niches to store personal belongings were incorporated into the walls. Sometimes, a small fountain or labrum can also be found in this room. In more luxurious bathhouses, the dressing room was also heated by a hypocaust.
Balaneion (βαλανεῖον)	A Greek-style bathhouse. In ancient literature, it could refer to both publicly and privately owned baths. The building characteristically consisted of one or more round rooms (tholoi) with single-person bathtubs placed against the walls. These tubs could be hip-baths (or sitz-baths) with an integrated seat, or long baths resembling modern tubs. In some Hellenistic-period examples, large heated pools (alvei) for communal use have been found (e.g. in Syracuse). These could be heated by a type of proto-hypocaust, consisting of a single underground channel that was heated by a furnace.
Bal(i)neum (pl. balnea)	The original Latin term to denote a bathhouse, whether public or private. The meaning of the word shifted during the early Imperial period, when the term thermae was introduced, but the difference between the two terms is still the subject of scholarly debate and the textual and epigraphic evidence does not permit to make a clear distinction. Possibly, balnea were privately owned and the owner had to buy a permit to use the public water supply. In modern research, the term balnea is mainly used to designate modest neighbourhood baths.
Balneum virile / muliebre	A bath building reserved for men or women. Sometimes a building will have two distinct, separate wings for each sex, but it also happened that a single building had separate opening hours for men and women.
Balneaticum	Entrance fee for baths in Italy. There is evidence for other admission fees of varying price depending on location and the gender of the patron (Nielsen 1993, 132). In Italy, during the late Republican and early Imperial periods, ancient sources reference a quadrans as a standard fee to use bathing facilities whose entrance costs were not covered by tax or benefactors (Nielsen 1993, 131-135; Fagan 1999, 160-161).
Balneator	A vague title that could be used for anyone working in the baths. In smaller baths, there was probably one such balneator who was a Jack-of-all-trades. His duties could include anointing, massaging and pouring water over the bathers, or even firing the furnace. In larger baths, these tasks were performed by several specialised staff members.
Baptisterium	An infrequently used term for a pool, generally a piscina or a natatio. The word is derived from the Greek verb βαπτίζω (to dip). In Late Antiquity, it was used as a term to designate the pool (or chapel) in which catechumens received the sacrament of baptism.
Basilica thermarum	Large rectangular halls, often with a peristyle (colonnaded court) and hence resembling the secular basilica. Such halls were usually found in large baths of the Imperial type, flanking the frigidarium. The walls often had recesses or apsidal exedrae in which statues were displayed. The basilica stood in connection with the apodyteria and the frigidarium, and was probably used as an exercise court, and more generally as a meeting place.
Bessales (sg. bessalis)	Square bricks measuring ⅔ of a Roman foot, or c. 20 cm. They are commonly used in the hypocausts of baths for the construction of the pilae.
Bipedales (sg. bipedalis)	Large square ceramic bricks measuring two Roman feet, or c. 59.2 cm. In baths, they were often used to span the gap between the hypocaust pillars (pilae), so the distance between two pillars was restricted to circa 60 cm centre-to-centre.
Brazier	Portable stove for holding burning charcoal, used to heat up a room. Such portable heat sources were often used in the dressing rooms (apodyteria) or dry sweat rooms (laconica) of bathhouses.
Brick	Ceramic building element used mainly for structural supporting elements (e.g. walls, pilae, or suspensura) of construction, as opposed to tile. The Roman bricks commonly used in baths tend to be thinner and larger than modern bricks. See bessales, sesquipedales, bipedales.
Caldarium (pl. caldaria) (often styled calidarium in Italian-language publications)	The hot room of a Roman-style bathhouse. It could have different forms. In the early bathhouses, it often had a rectangular plan with one apsidal ending for the labrum (see schola labri). In later times, it was often cruciform or round. The room was heated by a hypocaust and its walls lined with tubuli, and had at least one warm water pool (alveus) for communal use. The caldarium was usually oriented to the south to benefit from the light and heat of the afternoon sun; for this reason, it often projected out of the main building.
Calida piscina (or piscina calida)	A large swimming pool heated by a hypocaust. In the centre of the pool, a metal container (samovar) connected to the hypocaust could be sunk into the bottom to ensure the continuous heating of the water. These pools are uncommon and mainly found in more luxurious bathhouses (both public and private). They were always confined to a separate room connected with the tepidarium or the caldarium.
Capsarius	A cloakroom attendant in the baths. His prime concern was to guard the clothes and personal belongings of the bathers.
Castellum aquae	A reservoir at the end of an aqueduct that was used to distribute water to the different parts of the city.
Cella solearis (or soliaris)	A Latin term found mainly in North African inscriptions, possibly designating a heated hall or the caldarium. Not to be confused with solarium.
Claustrum	A Latin term literally meaning barrier. In an architectural sense, it can mean a lock or a grating in a window opening.
Destrictarium	A room in which the bathers could scrape (destringere) the mixture of oil, sweat and dirt off the skin with a strigil (sickle-shaped scraper). The room had no specific features. The term itself is only attested in an inscription from the Stabian Baths of Pompeii (CIL X, 829), but has found its way into the vocabulary of modern research.
Exedra (pl. exedrae)	An extension of the room, often semicircular in shape, that often contained benches or niches for statues. Exedrae could be used for a variety of purposes, including as libraries or lecture halls. In baths, they are often found in connection to the palaestra or to the perimeter walls (of the thermae).
Fistula (pl. fistulae)	A pipe or conduit; in baths, it was often made of lead. Many fistulae carry the names of the craftspeople who made them, the workshops that produced them, and/or even the ultimate owners of the structure into which the pipes were laid.
Frigidarium (pl. frigidaria)	The cold room of a Roman-style bathhouse. It appeared in the first century BC and soon became the largest room in the baths. It contained one or more cold-water immersion pools (piscinae). In smaller baths, the frigidarium could also serve as dressing room. It was normally rectangular in shape and connected to the apodyterium and the tepidarium.
Gymnasium (pl. gymnasia)	In the Greek-Hellenistic world, the gymnasium was an athletic training ground where the male youth was also educated. It evolved from an open space to an enclosed exercise court with surrounding classrooms and fountain houses. In some larger cities, the gymnasium also had basic washing facilities. During the Roman period in Asia Minor, the gymnasium merged with the public bathhouse, forming a specific architectural type usually referred to as bath-gymnasium. In Egypt, the term is also used to designate a bathhouse.
Heliocaminus	The term used by scholars to denote a room for sunbathing, although the few textual attestations do not mention this word in direct connection to a bathhouse. Alternatively, the word solarium is sometimes used, even if this term normally designates a sundial. On top of being oriented towards the south for maximal sunshine, such a room is also supposed to have had large windows.
Hip-bath (or sitzbath)	A tub made of stone or terracotta for individual immersion in balaneia (Greek-type baths), where it is usually found along the walls of the round tholos. It has a characteristic shape, with a seat at the high end and a small basin at the foot end; bathers would sit in it and an attendant would pour water over them. Individual tubs were also occasionally found in private bathrooms.
Hypocausis	A rare term to designate a furnace of the baths (Nielsen 1993, 162).
Hypocaust (also hypocaustum)	The heating system used in Roman-style bathhouses to heat rooms and pools. It consisted of a series of short columns/pillars (pilae) supporting the circulation floor (suspensura). The hollow space underneath the walking-level was heated by one or more furnaces. The hot gases of these furnaces heated the floor and hence the room above. The term is a latinised form of the Greek ὑπόκαυστον, meaning “heated from below”.
Kaisersaal (Imperial hall)	Modern German term to designate the large and richly decorated halls often found in large thermae, especially in the bath-gymnasia of Asia Minor. It was often connected to the palaestra and had one or more exedrae. The function may have been associated with the Imperial cult. The abundant use of marbles inspired the alternative term ‘Marmorsaal’ (marble hall).
Labrum (pl. labra)	A shallow basin elevated on a pedestal and containing water. The labrum is mainly found in the caldarium or sometimes in the apodyterium. Until the end of the 1st century AD, it was usual to place the labrum in an apsidal recess (schola labri) to enable several bathers to gather around the washing basin. The water was supplied by a spout in the centre of the basin or by a spout in the wall behind the labrum. In some cases the water was heated. The diameter of the labrum varied from 1 m to 2.5 m. The Greek term is λουτήρ or λουτήριον.
Laconicum	A round sweat room that was heated by charcoal braziers. This domed room often had seats or benches to accommodate the bathers. It usually stood in connection to the apodyterium or tepidarium. After the 1st century AD, the laconicum disappeared in favour of the sudatorium, which was heated by hypocaust and a wall heating system. The etymology of the term goes back to the Greek Λακωνικός (‘Laconian’), pointing to the link with the round sweat rooms found in Greek gymnasia.
Latrinae	Roman public toilets with a row of seats next to one another and a water channel running alongside them. They were often located within a bathhouse or next to it, using the same drainage system and sometimes benefiting from the water flushed from the pools of the baths.
Lavacrum	A term that probably denoted “a place where one could immerse oneself in water”, but later took on the meaning of bathhouse or even pool. In a Christian context, it was often used to designate the sacrament of baptism (lavacrum sacrum and lavacrum regenerationis). It was mainly used during Late Antiquity.
Lavatrina	A washroom or a simple bath room in a private residence. It was mainly used during the Republican period.
Louter (λουτήρ)	A shallow basin elevated on a pedestal and containing water. It is the Greek equivalent of the Latin labrum.
Loutron (λουτρόν)	Originally the washroom of a Greek gymnasium, the word gradually took on the meaning of bathhouse during Late Antiquity. It is closely related to the verb λουεῖν (to let water flow over something, to wash).
Marmorsaal	See kaisersaal.
Natatio (pl. natationes)	The large unheated swimming pool located in the cold section of the baths. It was often unroofed and surrounded by porticos, and had a depth up to 1.5 m. Such pools were mainly installed in the larger baths and demanded a considerable supply of water.
Noria	A term used to designate a treadwheel or waterwheel used as a water-lifting device in baths.
Nymphaeum (pl. nymphaea)	Originally a cave in which water surged, and which was dedicated to the Nymphs. In an architectural meaning, it denotes a monumental fountain. These could be freestanding or included in another structure, and they often had an elaborately decorated façade with columns, niches and statues. In Roman baths, nymphaea could form the monumental façade of a natatio or, in a more modest form, the background of a piscina. Alternatively, they were incorporated in the perimeter wall of larger bathhouses.
Opus africanum	A modern technical term denoting the masonry technique in which walls are constructed by alternating ashlar or orthostatic blocks with fillings of rubble concrete. The technique is mainly found in North Africa, as it was probably emerged from the Phoenician and Punic building tradition.
Opus caementicium	A modern technical term denoting Roman concrete. Roman concrete consisted of rough fragments of rock or tiles bound in mortar. The mixture was laid by hand (not poured like modern concrete) in between temporary timber formworks to create foundation walls, or was used in the core of brick-faced walls (opus testaceum and opus listatum).
Opus listatum	A modern technical term denoting the masonry technique in which the facing of a wall consists of alternating layers of brick with layers of small stone blocks. The core of the wall consists of opus caementicium. This technique is also called opus vittatum in modern literature.
Opus quadratum	An ancient technical term to denote a construction technique in which walls are constructed with large squared blocks of stone (ashlars) laid in regular courses, without the use of mortar.
Opus reticulatum	An ancient technical term to denote a construction technique in which the facing of a wall was made by inserting pyramidal stone blocks in an opus caementicium core, hence creating a reticulated, or net, pattern. The quoins (i.e. the outer corners of the walls) were often reinforced with bricks or stone blocks. The technique was mainly used in Central Italy during the (late) 1st century BC and 1st century AD, where the blocks were usually made of soft local tuff.
Opus sectile	A type of decorative mosaic work consisting of slabs or fragments of cut stone to form patterns. Geometric and floral patterns were very popular, and figurative scenes are found on occasion. It was often used to embellish pavements, less often walls.
Opus signinum	A type of revetment for floors and walls consisting of mortar, small pieces of stone and crushed terracotta, which gave it a pinkish colour. Its surface was often polished.
Opus spicatum	A type of pavement consisting of thin rectangular terracotta tiles laid sidewise in a herringbone pattern. It was introduced in the early Imperial period.
Opus testaceum	A modern technical term denoting the masonry technique in which the facing of a wall consists of regular layers (courses) of flat triangular bricks, embedded in an opus caementicium core.
Opus vittatum	See opus listatum.
Palaestra	An open courtyard attached to the bathhouse, often accessible from the frigidarium. The surface of the palaestra was usually made of beaten earth; it was sometimes paved, and occasionally laid out as a garden, as in the Imperial thermae of Rome. It was often rectangular in shape and was surrounded by a portico on one or several sides, behind which exedrae sometimes opened. The palaestra was used as an exercise yard and could therefore be equipped with running tracks and sports equipment. The natatio could also be located in or off the palaestra.
Peristyle (also peristylium)	A colonnade surrounding a court or a square. Peristyles were often found in gymnasia, palaestra and basilicae thermarum.
Pilae (sg. pila)	The small columns/pillars of a Roman-style hypocaust system that supported the circulation floor of the heated rooms. These pillars usually had a height comprised between 60 and 100 cm, and if spanned by bipedales, stood roughly 40 cm apart. The pillars were often made of round or square ceramic bricks bonded by mortar. Alternatively, stone monoliths or hollow ceramic tubes/cylinders were used.
Piscina	A Latin term for a pool. In modern research, it mainly denotes the cold pools of the frigidarium. The piscinae had internal steps for easy access and could be used by several bathers at the same time.
Piscina calida	See calida piscina.
Praefurnium (pl. praefurnia)	The service room that preceded a furnace. In modern research, it is often erroneously used to designate a furnace. These rooms lay on a lower level than the circulation floors of the heated rooms of the bathhouse, as the furnaces had to heat the hypocaust (i.e. the cavity underneath the suspensura).
Samovar or samowar	A term used in modern literature to describe a heating device found in calidae piscinae. It consisted of a cylindrical metal container placed into the centre of the floor and ensured, just as testudines in normal alvei, that the water of the pool could be kept warm. To heat this device directly, a service corridor ran underneath the pool to a furnace underneath the samovar. Only a few examples of this device are known, mainly in Italy.
Saqiyah	A mechanical waterwheel, powered by humans or animals, more commonly used in and local to Egypt and Palestine.
Schola labri	The apse in which a labrum was placed. It enabled several bathers to stand around the labrum at the same time. The apse was usually covered by a semi-dome which could be pierced by a round oculus (round window opening) to provide additional lighting.
Sesquipedales (sg. sesquipedalis)	Bricks measuring one and a half Roman feet (c. 44.4 cm) and often used in the construction of bathhouses.
Solarium	A Latin term meaning sundial; it is seldom used for a sun terrace in bathhouses (see also heliocaminus).
Solium (pl. solia)	An alternative term to denote a warm water pool (see alveus) in a Roman-style bathhouse. The word probably derived from the verb sedere (to sit), linking its origin to the Greek-style hip bathtubs that incorporated a seat.
Spacer (pins)	Spindle-shaped terracotta nails or pegs designed to support vertically set tiles at a distance from a masonry wall and thus create the void for wall heating systems. The pointed or chisel-shaped end were inserted directly in the mortar of the walls, while the opposite end typically contains grooves to hold the vertical tiles. Spacer pins were popular in parts of Asia Minor, Cyprus, and Crete, and were also used in Spain and North Africa, among other places.
Spacer (tubes/bobbins)	Cylindrical terracotta studs placed between the wall and vertically hung terracotta tiles to create a hollow space in which the hot gas coming from the hypocaust could circulate. The spacers as well as the tiles were attached to the wall by T-shaped iron nails, driven through the hollow centre of the spacer. This type of wall heating was popular in south Gaul and Britain, and examples have also been found in Asia Minor, Spain, Romania, and Corinth, among other places.
Sphaeristerium	An area for ball games, derived from the Greek word sphaira (σφαῖρα, ball). Judging from the mentions in ancient literature, it could be a hall or an open courtyard.
Strigil	A sickle-shaped hollow blade usually made out of metal, wood or bone, to scrape off dirt, oil and sweat after physical exercises or massages.
Sudatorium	A sweat room in a Roman-style bathhouse. It was derived from the verb sudare (to sweat). In modern research, sudatorium is used for a room with a hypocaust and wall heating, heated by its own furnace(s). It is often located between the tepidarium and the caldarium. In this room, the bathers sat on benches where they sweated out what was thought as bad bodily fluids. Sudatoria were rarely fitted with a pool.
Suspensura	The floor supported by the pilae as part of the hypocaust. This ‘suspended floor’ usually consisted of (from bottom to top): a layer of bipedales, a thick layer of waterproof mortar, a thin layer of mortar, and a marble or mosaic revetment. The total thickness could vary between 30 and 50 cm. Alternatively, the lower part of the suspensura could be made of brick arches that spanned the space between the pilae.
Taberna	Latin term to denote a shop, a shed or a booth. Tabernae were sometimes built against the outer walls of the palaestra and consisted of one or two rooms open to the street. The tabernae around baths could sell food, beverages and possibly bath-related items such as oil and nitrum (salt scrub).
Tegulae mammatae (sg. tegula mammata)	Literally meaning ‘nipple tiles’, these square or rectangular terracotta tiles had projecting bosses in the corners of one side, so that a cavity was created when placing these tiles vertically against a wall. The tiles were fixed to the wall with iron T-shaped clamps. The open space between wall and tiles connected with the hypocaust, enabling the hot gases to rise ‘inside’ the wall. This system of wall heating is mainly found in Republican and early Imperial baths, and was gradually replaced by tubuli.
Tepidarium	A tepid room in a Roman-style bathhouse. It could have different shapes and was located between the frigidarium and the caldarium,or between the frigidarium and the sudatorium. In this room, the bathers acclimatised to the heat before entering the hot rooms. Early tepidaria were heated with charcoal braziers, but from the Imperial period onwards, they were heated by a hypocaust. Sometimes the tepidarium had no wall heating, in an effort to maintain a lower temperature than in the caldarium. For the same reason, it was often indirectly heated by the furnace of the sudatorium or the caldarium. From the 2nd century onwards, the tepidarium sometimes had a small pool to enable the bathers to have a dip in tepid water, before plunging into the cold-water piscina of the frigidarium.
Tessera (pl. tesserae)	A small cube, tag or token. In an architectural context, the term is used to denote the small cubes used to compose mosaics. The tesserae were often made of stone, sometimes of glasspaste or terracotta.
Testudo (alvei)	A Latin term literally meaning a tortoise shell, it is also used as a technical term to denote the half-cylindrical metal container placed above a furnace, with its flat side facing down and in direct contact with the bottom of the alveus. The end towards the alveus was open: as the colder water in the pool sank towards the bottom, it was reheated inside the testudo and then rose again by convection. This cyclical process ensured that the water inside the alveus stayed warm.
Thermae	Latin term to denote a Roman-style bathhouse (only used in its plural form). It came into use during the 1st century AD as a way of demarcating a new type of bathhouse from the older balnea. There is still uncertainty about the exact difference between both terms. The most recurring hypotheses see thermae as the more luxurious bath buildings, often donated by the emperor, or as bathhouses run by civic authorities, benefiting from a free water supply. Parameters such as size and the presence of a palaestra do not seem to have been distinguishing features.
Thermae aestivales (or aestivae)	Latin term to denote Roman-style summer baths, as opposed to thermae hiemales. Both types of baths are often found close to each other, and they are sometimes structurally linked. Alternative terms are balneum or lavacrum aestivum. Some uncertainty remains as to the distinctive characteristics of these ‘seasonal’ baths. It seems that the summer baths had more and larger pools than the winter baths. In North African examples, the summer baths also had an open semicircular latrine. The duo summer–winter baths seems to have been popular in the warmer regions of the Mediterranean, such as the Italian Peninsula, the Iberian Peninsula, North Africa, and the Eastern provinces.
Thermae hiemales	Latin term to denote Roman-style winter baths, as opposed to thermae aestivales. Both types of baths are often found close to each other or are sometimes structurally linked. Alternative terms are balneum hiemale or balnearia hiberna. Some uncertainty remains as to the distinctive characteristics of these seasonal baths. It seems that the winter baths were smaller and had fewer and smaller pools than the summer baths. The heated section was also smaller, as heating large rooms in winter meant higher fuel costs. In known North African examples, the winter baths had closed rectangular latrines, as opposed to the large semicircular latrines of the summer baths. See also thermae aestivales.
Tholos (pl. tholoi) (θόλος)	A round room covered by a dome. This dome could have a circular opening in its centre to permit air and light to enter. In Greek-style baths, such rooms were often equipped with single-person hip-baths. In Roman-style baths, especially in early examples,  round rooms were first used as sweat rooms, heated by a brazier. In several Pompeian and Herculanean baths, this sweat room was later transformed into a cold pool.
Tile	Ceramic building material used mainly for non-structural elements of construction, such as the covering of floors, walls, or roofs, as opposed to brick.
Tubus fittilus (pl. tubi fittili)	Cylindrical or bottle-shaped ceramic building material used to construct walls and especially vaults. They were open at both ends, but wide at the bottom and narrow at the top so that they could fit into each other. The oldest examples date from the 3rd century BC, but they were mainly used from the 2nd century AD onwards. Often found in North Africa.
Tubulus (pl. tubuli) (also box-flue tile, esp. in Roman Britain)	Hollow ceramic tile, often box-like or cylindrical.In Roman-style baths, rows of superimposed tubuli were placed against the walls of heated rooms and connected to the hypocaust to create a heated wall. Chimney flues connected with the top row of tubuli ensured that the hot gases of the hypocaust were drawn into the tubuli. If the tubuli were not connected to a hypocaust, they served a mere insulation for the walls.
Tubulus cuneatus	Wedge-shaped tubulus used for the construction of vaults.
Unctorium	A room in which bathers could be anointed with oil, and possibly massaged. It had no special characteristics and could be connected to the palaestra, to the frigidarium or to one of the heated rooms. In some baths, the unctorium may have been heated.
Vestibulum (pl. vestibula)	An entrance court. In bath buildings, the first room entered by the bathers; it was often used as a lounge to relax or socialise before or after bathing.