1. The addition of a prefix, a suffix, or an infix to a word in order to create a new expression or a variation in the meaning: The affixation of the term "establish" with "ment" at the end of the verb, creates the noun, "establishment", which then has a different understanding.
2. The formation of a word by means of an affix: The affixation of  "discourage" uses the prefix "dis", which is added to the root "courage" and alters the content of the term.

The effect of attaching an affixation to an expression transforms the content of the meaning or part of speech; for example, "recreation" (noun) can be changed to "recreational" (adjective).

In his English class at school, Jake learned how to convert the content of several words by using the method of affixation, which changes them from one part of speech to another one or changes their meanings completely.