This is the 5982nd most frequent Russian word.
сильную
The Russian word "сильную" means "strong" (feminine, accusative case).
In this sentence, 'сильную' is used as an adjective modifying the noun 'боль' (pain), indicating the intensity of the feeling.
Она почувствовала сильную боль в ноге.
She felt a strong pain in her leg.
Here, 'сильную' is an adjective describing the noun 'бурю' (storm), referring to its power or magnitude.
Мы видели сильную бурю на горизонте.
We saw a strong storm on the horizon.
In this context, 'сильную' modifies the noun 'поддержку' (support), depicting the substantial or effective nature of the assistance.