This is the 3582nd most frequent Russian word.
сложные
"Complex" or "difficult."
Used to describe something as being intricate or detailed.
Эта книга содержит сложные концепции.
This book contains complex concepts.
Used to indicate problems or exercises that require a deep understanding or effort.
Они решили сложные задачи на экзамене.
They solved complex problems in the exam.
Describes emotional or interpersonal states that are challenging or problematic.