The first use of aircraft registrations was based on the radio callsigns allocated at the London International Radiotelegraphic Conference in 1913. This was modified by agreement by the International Bureau at Berne and published on April 23, 1913. Although initial allocations were not specifically for aircraft but for any radio user, the International Air Navigation Convention held in Paris in 1919 made allocations specifically for aircraft registrations based on the 1913 callsign list. The agreement stipulated that the nationality marks were to be followed by a hyphen then a group of four letters that must include a vowel (and for the convention Y was considered to be a vowel).
The marking have been amended and added to over the years and the allocations and standard are managed by the International Civil Aviation Organization (ICAO).
Article 20 of the Chicago Convention on International Civil Aviation (signed in 1944) requires that all signatory countries register aircraft over a certain weight with a national aviation authority. Upon registration, the aircraft receives its unique "registration" which must be displayed prominently on the aircraft.

Cuando se habla de registro se utiliza el sustantivo "registration".
Este enlace aclara el concepto

http://www.aerospaceweb.org/question/history/q0257.shtml