I created a new domain called 'Object'. I tried to assign it to a field. It did not work: it simply would not appear in the domain field of the field properties dialog after I clicked it. I then tried to delete this domain. This also did not work. I created a new domain called 'Obj' and this performed correctly. Please advise. Possibly, ArcCatalog/Map/etc should inform users automatically when they try to name a domain 'Object' that it will not work. Please advise me if it will ever be possible to delete this domain or if I will have to recreate the whole file geodatabase. Version: ArcGIS Desktop 10.5.1.