R

Reactant- Something that is capable of reacting to something. Reaction-A response to a change Region-an area Role-a part or function
 * Online Definition: Reactant on Wikipedia
 * [[image:http://farm3.static.flickr.com/2306/1935293760_c4253b94f8.jpg?v=0 width="165" height="105"]]
 * Photo:[|Chemistry by Brian Hathcock]
 * Online Definition: [|Reaction on Wikipedia]
 * photo:Chemical by chemistry lab euthman
 * Online Definition:[|Region on wikipedia]
 * [[image:http://farm1.static.flickr.com/71/153790855_e8b76eb9e8.jpg?v=0 width="178" height="146" link="http://en.wikipedia.org/wiki/Role"]]Online Definition:[|Role on wikip][|edia]