This is the 4954th most frequent Russian word.
контрольные
"Контрольные" means "tests" or "exams" (typically in an academic context).
The word 'контрольные' is used as an adjective describing 'работы' (tests), meaning tests for assessment.
Сегодня мы пишем контрольные работы.
Today we are taking control tests.
The word 'контрольные' is used as an adjective describing 'задачи' (problems), indicating problems meant for verification of knowledge.
Контрольные задачи помогают закрепить материал.
Control problems help reinforce the material.
The word 'контрольные' is used as a noun, referring to the control tests or assignments themselves.