It is of an outstanding importance that, when signing a bilateral or multilateral treaty or convention, in which one of the legal terms such as national , citizen, subject, ressortissant and the like is involved, a correct and proper expression is selected and adopted in it. This is because the coverage of some of these terms in the laws of certain countries is much different from those in other countries.
This research aimed at conducting a study on the subjects of all legal terms and expressions similar to "national and nationality" in the laws of Iran, UK, USA and France in order to show their similarities and differences.
The results showed all the terms used in Iranian law hold the general meaning of national and nationality, witch cover equally all Iranians; whereas in UKs "1981 Nationality Act", three different categories of internal and overseas nationalities and citizenships are recognized. In the US legal system, the citizens and nationals are divided into two different groups: "the US citizens and" "the nationals of United States". The number of subjects and social rights of the former are incompatible to the latter. Finally, in French law, there are four similar expressions each of which varys in number of subjects as well as social rights