As this is not a concept I'm yet familiar with and as both tags have tag wikis I don't want to just step in and retag the questions myself. Here's what the wiki excerpts currently have to say:
reification × 16
Reification refers to process of taking an abstract concept and making a concrete representation out of it.
reify × 7
To "reify" means to take an abstract concept and make a concrete representation out of it. For example, in Lisp lambdas allow you to reify the concepts of procedure abstraction and application.
(Neither tag has a full wiki, just an excerpt each.)