Which word describes deep, extensive learning?

The term that best describes deep, extensive learning is "erudition." This word specifically refers to a profound, comprehensive level of knowledge that is gained through extensive reading and study. Erudition goes beyond simple knowledge; it implies a depth of understanding and intellectual breadth across various subjects.

While "knowledge" indicates familiarity or awareness of facts, information, or skills, it does not necessarily convey the idea of depth and comprehensive learning. "Wisdom," on the other hand, is often associated with the judicious application of knowledge and experience rather than the accumulation of learning itself. Lastly, "insight" refers to the ability to gain an accurate understanding of something, but it does not capture the extensive nature of learning that "erudition" embodies. Therefore, "erudition" is the most fitting term for describing deep, extensive learning.