Ahmadi already provided the definitions, but of these words, generally, 'perceptive' and 'astute' are commonly used. 'Sagacious' is quite rarely used, and the rest are very, very rarely encountered in modern usage. As a strategy, personally, I'd focus on using 'perceptive' and 'astute'-- as they are quite useful and generally applicable--whereas 'Sagacious' can be useful but will have limited application.

Certainly! All of these words are adjectives used to describe someone's ability to perceive, understand, and discern things. However, they do have some nuanced differences: Percipient: Definition: Having a clear and keen perception; perceptive or observant. Usage: This term emphasizes the ability to perceive and become aware of things or situations accurately. Perspicacious: Definition: Having keen mental perception and understanding; able to see things clearly and quickly. Usage: This word emphasizes the capacity to understand complex or subtle issues and make insightful judgments. Perceptive: Definition: Having or showing a keen awareness, insight, or understanding of things. Usage: This word generally implies being able to notice and comprehend subtle details or aspects of situations or people. Sagacious: Definition: Having or showing good judgment, wisdom, and keen perception. Usage: This term emphasizes the possession of practical wisdom and the ability to make sound decisions. Astute: Definition: Having an ability to accurately assess situations or people and make shrewd decisions. Usage: This word highlights the ability to analyze and understand situations quickly and make clever, often strategic, choices. In summary, while all these words relate to the ability to perceive and understand, they differ in the specific aspects they emphasize. "Percipient" focuses on being observant and aware, "perspicacious" on insightful understanding, "perceptive" on keen awareness, "sagacious" on wise judgment, and "astute" on clever and strategic decision-making.

Like many “high register” words, ‘sagacious’ derives from old French ‘la sagesse’ (wisdom). I’d second Matt’s comment. 'Perceptive' and 'astute' are the terms most often used by educated native speakers. The others you may come across in literature, but in spoken language they’re very rarely used.

A quick way to understand the differences between these words is to look them up in an etymological dictionary like etymonline.