This is the 758th most frequent Ukrainian word.
розслідування
Investigation.
The word 'розслідування' is again a noun and is used to denote the active process of investigating, carried out by law enforcement.
Поліція проводить розслідування, щоб встановити причини інциденту.
The police are conducting an investigation to determine the causes of the incident.
In this sentence, 'розслідування' refers to an analytical procedure undertaken by journalists to uncover important information for a report.
Журналістське розслідування виявило багато нових фактів.
The journalistic investigation revealed many new facts.
The word 'розслідування' is used here as a noun meaning 'investigation', referring to the formal analysis or inquiry into a particular matter.