This is the 14446th most frequent Russian word.
официальном
"Official" (pertaining to formal or authorized).
'Официальном' here describes the required format of the document, meaning it conforms to the rules or standards of a formal procedure.
Этот документ должен быть представлен в официальном формате.
This document must be submitted in an official format.
'Официальном' in this context characterizes the nature of the event, indicating it is organized formally or officially.
На официальном мероприятии присутствовали важные государственные деятели.
Important state officials attended the official event.
Here, 'официальном' specifies the designated or authorized status of the location for formal events.