This is the 11645th most frequent Russian word.
жесткой
"Жесткой" means "rigid," "tough," or "harsh" in English, depending on context.
In this sentence, 'жесткую' (strict) is used to describe the nature of the diet, emphasizing its rigorous and harsh requirements.
Она выбрала жесткую диету, чтобы быстро сбросить вес.
She chose a strict diet to lose weight quickly.
Here, 'жесткой' (sharp) is used to describe the intensity of the criticism, illustrating its biting and stringent quality.
Жесткой критикой она заставила нас задуматься о наших ошибках.
With sharp criticism, she made us reflect on our mistakes.
In this case, 'жесткой' (tough) is employed to signify the severity of the confrontation, bringing attention to its uncompromising and hard nature.