This is the 2626th most frequent Russian word.
уголовных
"Criminal" (adjective related to crime).
Here, 'уголовных' is an adjective describing 'дел', indicating their criminal nature.
Уголовных дел становится всё больше.
Criminal cases are becoming more numerous.
In this sentence, 'уголовных' is a descriptive adjective modifying 'преступлений', marking them as related to crime.
Студенты изучают теории уголовных преступлений.
The students study theories of criminal crimes.
Here, 'уголовных' is used as an adjective for 'событий', showing their relation to criminal actions or affairs.