What does the word improvement mean?

Usage examples for improvement

  1. But tell me, would this treatment produce a similar improvement if the symptoms were due to disease?" – The Mystery of 31 New Inn by R. Austin Freeman
  2. He always had the cause of the oppressed colored people warmly at heart, and was desirous to do everything in his power for their improvement and elevation. – The Freedmen's Book by Lydia Maria Child