The Halachic Definition of Reshus Harabim
Reshus harabim is one of the four domains of Shabbos. Carrying four amos within a reshus harabim, or transferring between a reshus harabim and a reshus hayachid, is prohibited min haTorah. Its definition is therefore fundamental to every later question about an eruv.
The definition is sometimes presented as though one feature settles everything: a street is sixteen amos wide, a road is or is not straight, or six hundred thousand people do or do not pass through an area. The classical sources give a more structured picture. Some features describe the public way itself, some describe its public function, and some concern the surrounding city and its mechitzos. The requirement of shishim ribo is itself a major dispute.
Seratya, platya, and mefulash passageways
The basic Talmudic formulation is concise:
איזו היא רשות הרבים? סרטיא ופלטיא גדולה ומבואות המפולשין, זו היא רשות הרבים גמורה.
What is reshus harabim? A seratya, a large platya, and mefulash passageways. This is a full reshus harabim.
(Shabbos 6a.)
These are functional categories of public space.
A seratya is a major road, the kind of road used for broad public passage. A platya is a large public square or marketplace. A mavoi mefulash is a passageway open through to another public way. Chazal's examples are therefore roads and spaces built around the movement and gathering of the public.
The later Poskim translate those categories into more exact physical rules. Width matters. Roofing matters. The manner in which a road passes through an area matters. Walls and gates can change the status of the larger area. The public character of the road remains part of the subject throughout.
The terminology also warns against an overly literal modern translation. A present-day “marketplace” is not automatically a platya, and a road called an “avenue” is not automatically a seratya. The halachic features of the place must be examined.
Sixteen amos and an uncovered public way
The Rambam writes:
ובלבד שיהיה רוחב הדרך שש עשרה אמה, ולא תהיה עליו תקרה.
The road must be sixteen amos wide and may not be roofed.
(Hilchos Shabbos 14:1.)
The Shulchan Aruch and Alter Rebbe likewise begin their practical definition with streets and marketplaces that are sixteen amos wide and uncovered. The sixteen-amah measure is rooted in the public way of the machaneh in the midbar, which provides the model for the melachos and domains of Shabbos.
This requirement attaches naturally to the way through which the public travels. It does not mean that every point in an entire city has to be sixteen amos wide before any part of the city can contain a reshus harabim. A metropolis may contain major roads, narrow side streets, alleys, squares, private compounds, and enclosed areas at the same time.
Modern roads create further measurement questions. A single avenue can contain a central median, traffic lanes in both directions, parking lanes, bus lanes, bicycle lanes, safety islands, and sidewalks. Whether a feature divides the road halachically or remains part of one public way depends on the laws of the relevant partitions and surfaces. Those measurements are treated in detail on the page devoted to sixteen amos.
The second element in the Rambam's sentence, that the way is not roofed, is equally basic. A covered public passage does not have the same status as an open public road merely because many people use it. The laws of covered passages have their own details, but the classical definition of the outdoor public road is expressly uncovered.
What mefulash means
The word mefulash means that a passage is open through or passes through. In the laws of eruvin it appears in more than one setting, and those settings have to be distinguished.
The Shulchan Aruch and Alter Rebbe discuss a city surrounded by a wall. A wall would ordinarily create an enclosure. If a sixteen-amah public road passes through the city from one gate to the opposite gate, the road can retain the status of reshus harabim when the gates remain open. The Alter Rebbe describes the gates in this case as aligned with one another.
That formulation has sometimes led to a broader question: does every public road, even in an unwalled city, cease to be a reshus harabim unless it is perfectly straight from one end to the other?
Rav Moshe Feinstein addresses this directly in Igros Moshe, Orach Chayim V:28. In his analysis of Rashi, the aligned-gate requirement is connected to the special case of a walled city. The wall is what creates the possibility of enclosing the city; a road running directly through its openings can prevent that enclosure from removing the road's public-domain status. Rav Moshe therefore explains that an unwalled city does not require opposite city gates or a straight route out of the city as a condition for a sixteen-amah public road to be a reshus harabim.
This distinction keeps two questions from being collapsed into one. One question asks whether a road itself is a public thoroughfare. Another asks whether surrounding walls enclose that road and, if so, whether a gate-to-gate opening defeats or limits the enclosure.
The detailed disagreements over straightness, bends, T-junctions, dead ends, and roads that open into other roads belong to the page on mefulash.
Public passage and access
The names used by Chazal already describe a reshus that belongs to public life: the major road, the large public square, and the passageway open through to public ways. Public passage is therefore part of the character of reshus harabim.
This is broader than the name on a deed or the identity of the government agency responsible for a street. Halacha is concerned with the actual character of the way. A road that is genuinely open and used by the public presents a different question from a private compound with controlled entry, even when both appear broad and paved on a map.
Conversely, heavy foot or vehicle traffic does not by itself answer every other requirement. A busy passage may be too narrow. It may be roofed. It may lie within effective mechitzos. Its entrances may be controlled in a manner that changes the analysis. Public use works together with the other elements of the definition.
There are also several kinds of restrictions. A gate that is physically present is one matter. A rule restricting who may enter is another. A road closed at particular hours, a military or industrial compound, a toll road, and a residential street with ordinary traffic controls do not necessarily share one halachic status. The dedicated page on public access treats those distinctions.
The shishim-ribo dispute
The best-known dispute concerns shishim ribo, six hundred thousand people.
Rashi defines an ir shel yachid in Eruvin 59a by the absence of regular entry of shishim ribo and explains that such a city does not resemble the public domain of the machaneh in the midbar. Tosafos, on Eruvin 6a, likewise records the requirement and cites the Halachos Gedolos. On this approach, the scale of public passage in the midbar becomes part of the definition of a full reshus harabim.
Other Rishonim do not include this requirement. The Rambam's definition in Hilchos Shabbos 14:1 lists the public way and its sixteen-amah width without mentioning six hundred thousand. The Ramban, discussing Rashi's position in Eruvin, objects that a six-hundred-thousand condition is not stated in the Gemara:
ולא ידענו מנין לו לרש״י כן שלא הוזכר בתלמוד בשום מקום.
We do not know Rashi's source for this, since it is not mentioned in the Talmud.
(Chiddushei HaRamban, Eruvin 59a.)
The Ramban then notes that the requirement is found in the Halachos Gedolos. His objection therefore identifies a genuine dispute in the early sources. It does not make the six-hundred-thousand view a late innovation.
The Shulchan Aruch presents the issue in two stages. He first gives the physical definition of wide, uncovered public streets and marketplaces. He then records a yesh omrim that an area through which shishim ribo do not pass each day is not a reshus harabim.
That structure matters. A statement such as “there is no reshus harabim without six hundred thousand” follows one major position. It is not the only definition found among the Rishonim or in the codes.
The Alter Rebbe's formulation
The Alter Rebbe follows the same basic structure in Shulchan Aruch, Orach Chayim 345:11. He first defines streets and marketplaces sixteen amos wide, together with the laws of walls, gate-to-gate passage, intercity roads, and related public ways. He then adds:
ויש אומרים שכל שאין ששים רבוא עוברים בו בכל יום אינו רשות הרבים אלא כרמלית.
There are authorities who say that where six hundred thousand do not pass each day, the area is a karmelis rather than a reshus harabim.
He continues that the custom had spread to rely on this opinion and to say that there was no full reshus harabim in his time, and he adds that a yerei Shamayim should be stringent for himself.
Several separate questions arise from those few lines. What does “pass through” mean? Must the six hundred thousand use one point, one street, or a larger network? What period is relevant? How does this opinion relate to the physical criteria stated immediately before it? How should the Alter Rebbe's description of contemporary practice be applied to a city unlike the towns of his time?
Those questions require a fuller treatment. The definitions of shishim ribo and the Alter Rebbe's discussion of “no reshus harabim today” are therefore treated separately. Population and traffic calculations for New York also belong to their own pages.
Street, route, and city
A modern city contains several possible units of analysis, and different halachic criteria attach to different units.
The sixteen-amah requirement describes a road or public way. The question of roofing likewise concerns the particular place through which one carries. Mefulash can describe a passageway connecting public ways, while the aligned-gate discussion concerns the relationship between a public road and a surrounding city wall. Existing mechitzos may surround a neighborhood, district, island, or city. The shishim-ribo requirement adds its own disputed question about the relevant flow of people.
This is why population figures alone cannot define the status of every street. The population of a city does not tell us the width of a particular road, whether that road is public, or whether effective mechitzos surround it. The reverse is also true. Finding a sixteen-amah road does not settle how shishim ribo is understood or whether an existing enclosure changes the domain.
Rav Moshe's analysis of walled and unwalled cities gives a concrete example. A walled city raises the question of whether the road pierces the enclosure from aligned gates. In an unwalled city, Rav Moshe does not require an imaginary pair of city gates before a public road can be classified. The criterion belongs to the setting that produced it.
The broader question of street versus city requires a fuller treatment because it also affects the various readings of shishim ribo and the analysis of large urban networks.
Walls, gates, and the force of mechitzos
The definition of reshus harabim cannot be separated entirely from the laws of mechitzos, because a valid enclosure can change the status of the enclosed area.
The Rambam states that a city surrounded by a wall whose gates are closed at night is a reshus hayachid. The Shulchan Aruch and Alter Rebbe likewise discuss the effect of walls and gates, and the circumstances in which a public road running through the city remains a reshus harabim.
The Gemara in Eruvin 22a highlights כוחן של מחיצות, the halachic force of partitions, in a case where a public road crosses an area enclosed by the special partitions surrounding wells. That sugya is one of the central sources for the relationship between public traffic and existing mechitzos.
It does not follow that every line on a map counts as a halachic wall. A riverbank, railway structure, retaining wall, fence, building line, highway barrier, or natural slope must satisfy the relevant laws of mechitzos. Breaks and openings have their own measurements. A road crossing the perimeter can raise the law of delasos. These questions belong to physical enclosure and gates and delasos.
There is a further practical consequence. The Alter Rebbe rules in Orach Chayim 364:4 that an ordinary tzuras hapesach is not Rabbinically sufficient to permit carrying in a full reshus harabim, even though a tzuras hapesach has the status of a complete mechitza on the Torah level. A full reshus harabim requires the law of delasos. Thus the classification of the domain comes before the choice of eruv structure.
What must be kept separate in a modern city
A sound modern-city analysis keeps four groups of questions distinct while allowing them to interact.
First are the properties of the road: sixteen-amah width, roofing, and the physical course of the public way. Second is its public character: who can use it, how it connects to other public ways, and whether restrictions on access have halachic significance. Third is the larger enclosure: existing walls or other mechitzos, breaches, openings, and gates. Fourth is the dispute over shishim ribo and the precise unit of population or passage required by the authorities who adopt that condition.
The sequence prevents circular reasoning. One cannot prove that a road is a karmelis simply because an ordinary tzuras hapesach has been erected around it; whether that tzuras hapesach is sufficient depends on the road's prior classification. One likewise cannot classify an entire city from a population figure without examining the physical public ways and any relevant enclosure.
For a particular city, the general definitions must then be applied to actual facts: street dimensions, route geometry, access, physical boundaries, gates, traffic, and population. The pages on Manhattan, Brooklyn, and Crown Heights perform that application separately. This page supplies the definitions those discussions require without importing their conclusions into the general halacha.