This is the 18451st most frequent Russian word.
эффективная
Effective.
The adjective 'эффективная' describes the noun 'стратегия', indicating that the strategy is capable of producing the desired result efficiently.
Эффективная стратегия помогла нам достичь успеха.
An effective strategy helped us achieve success.
Here, 'эффективную' (accusative singular feminine form of the adjective 'эффективная') modifies 'программу', specifying that the program is designed to achieve its goals efficiently.
Она разработала эффективную программу для обучения.
She developed an effective program for training.
The word 'эффективны' (plural form of the adjective 'эффективный') compares the effectiveness of two groups of methods, showing its usage in comparative context.