For a physical object (like a knife):
* Острый (ostryy) - This is the most common and general word for "sharp."
* Резкий (rezkiy) - This implies a strong, sudden sharpness.
For a sound:
* Резкий (rezkiy) - Used for a sharp, sudden, or piercing sound.
For a person's mind:
* Проницательный (pronitsatel'nyy) - Means "sharp-witted," "perceptive," or "insightful."
* Острый (ostryy) - Can also be used for a person's sharp mind, especially in a negative context (e.g., "ostryy yazyk" - sharp tongue).
For a feeling:
* Резкий (rezkiy) - Can be used for a sharp, sudden feeling, like a pain.
It's important to choose the right word based on the context to convey the specific meaning of "sharp."