In this chapter, we group the available input reactor project input options (keywords) according to the Reactor Model with which they may be used. Note that many keywords can be used with several different Reactor Models and that there are a few cases where keywords that share the same name may have different meanings for different Reactor Models. General information about keyword syntax and rules is given in CHEMKIN Project Input: Keyword Syntax and Rules. A detailed, alphabetical listing of all keywords is given in Alphabetical Listing of Project Input Keywords. This chapter is meant to serve as a quick cross-reference to the more detailed information in Alphabetical Listing of Project Input Keywords.