This is the 5381st most frequent Russian word.
официального
"Official."
In this case, 'официального' is used as an adjective describing 'мероприятия' (event), meaning official.
Я получил приглашение на официального мероприятия.
I received an invitation to an official event.
Here, 'официального' modifies 'утверждения' (approval), indicating that the approval is formal or recognized by an authority.
Документ не имеет официального утверждения.
The document lacks official approval.
In this sentence, 'официального' describes 'подтверждения' (confirmation), emphasizing the necessity for a formal or authoritative validation.