A community Eruv (Hebrew: ערוב mixture, also transliterated as Eiruv or Erub, plural: Eruvin) refers to the legal aggregation or "mixture" under Jewish religious property law of separate parcels of property meeting certain requirements into a single parcel held in common by all the holders of the original parcels, which enables Jews who observe the traditional rules concerning Shabbat to carry children and belongings anywhere within the jointly held property without transgressing the prohibition against carrying a burden across a property line on the Jewish sabbath. The legal aggregation is set up to have effect on the Sabbath day only; on other days of the week, including Yom Tov (with the exception of Yom Kippur), ordinary property ownership applies. A valid aggregation has a number of requirements including an agreement among the property-holders and an aggregation ritual.
One of the requirements of a valid aggregation is that all the parcels must lie within a chatzer, or walled courtyard. For this reason, this type of aggregation is more properly known as an eruv chatzerot (Hebrew: ערוב חצרות), an "aggregation of courtyards," to distinguish it from other types of rabbinically-ordained mixture procedures which also have the name eruv.
