A particular instance, version, or school thereof; a particular theory of knowledge.
The branch of philosophy dealing with the study of knowledge; theory of knowledge, asking such questions as "What is knowledge?", "How is knowledge acquired?", "What do people know?", "How do we know what we know?", "How do we know it is true?", and so on.
Knowledge about types, domains, functions, or preconditions of knowledge.
Knowledge about knowledge itself (for example, epistemologic awareness).