This is the 3570th most frequent Russian word.
сильной
The Russian word "сильной" means "strong" (feminine form, instrumental case).
As an adjective describing a feminine noun, referring to someone's personality strengths.
Она является сильной личностью.
She is a strong personality.
As an adjective describing a feminine noun in its nominative case, referring to strategic effectiveness.
Для успешной кампании необходима сильная стратегия.
For a successful campaign, a strong strategy is required.
As an adjective in the accusative case describing a masculine noun, indicating the intensity of the weather.