Socialization: Tacit to tacit. Knowledge is passed on through practice, guidance, imitation, and observation.
Externalization: Tacit to explicit. This is deemed as a particularly difficult and often particularly important conversion mechanism. Tacit knowledge is codified into documents, manuals, etc. so that it can spread more easily through the organization. Since tacit knowledge can be virtually impossible to codify, the extent of this knowledge conversion mechanism is debatable. The use of metaphor is cited as an important externalization mechanism.
Combination: Explicit to explicit. This is the simplest form. Codified knowledge sources (e.g. documents) are combined to create new knowledge.
Internalization: Explicit to tacit. As explicit sources are used and learned, the knowledge is internalized, modifying the user’s existing tacit knowledge.