We define a learning tutor as being an intelligent agent that learns from human tutors and then tutors human learners. The notion of a learning tutor provides a conceptual framework for integrating the fields of intelligent tutoring-learning environments and machine learning-based knowledge acquisition. We present the conceptual framework of a learning tutor that adapts and integrates major portions of two existing successful systems, one of each kind, originally built separately by the respective authors. It is being developed and applied to the domains of software use and chemistry. 1 An Approach to Unification Machine Learning-based Knowledge Acquisition (MLKA) systems and Intelligent Tutoring-Learning Environments (ITLE) are engaged in the same activity except for a role reversal: one system learns from humans and the other helps humans learn. Nevertheless, the two kinds of systems, as well as the fields of Machine Learning and Intelligent Tutoring Systems, have grown up separately...