The gemara reads "In a public domain or in a courtyard that is not either of them." It really means simta and not public domain. Then why does it say reshus harabim?
Barry Epstein, Dallas, USA
The relevant characteristic here is that it is a place that the public has the rights to use. Therefore, it is called a "Reshus ha'Rabim." As far as property rights go, a Simta qualifies as a "Reshus ha'Rabim." However, the more specific usage of the term "Reshus ha'Rabim" -- such as a public domain as far as Shabbos is concerned -- is unacceptable for Kinyan for other reasons.
"Reshus ha'Rabim" has different definitions as it relates to various different Halachos. For example, a "Reshus ha'Rabim" with regard to the laws of Tum'ah is defined as any area in which there are three people.