Accessioning an object or item is the action of officially adding it to a museum's collection.
When an object gets admitted to a museum's collection, it is recorded in the museum's register and given an accession number by which it can be identified in all future documentation and references.
In BrazilAccessioning is not understood in Brazil in the same way as in the English spearkers countries. In the brazilian context, accessioning is part of the acquistion process. That is, when an object is acquired, it is already considered as officially part of the collection. Assigning a registration number happens shortly after the acquistion procedures are finalized, normally when the object is inscribed in the museum´s catalog or register.
Another interesting point to discuss and that may serve to illustrate even more the differences between the two contexts is that, in the English spearkers countries, it is very usual to find in the literature that acquisition represents the moment when an object enters to a museum, but its destination remains to be discussed (considering the fact that it may become part of the collection or will turn into something else as a handling collection/educational material). In case of the object is indicated to compose the museum collection, it will be accessioned. But this is not a very common or weadspread practice in Brazil, since the objects, when acquired, are usually indicated direct and exclusively for the museum´s collection.