Sentence:  Sometimes when there are many outcomes for a single trial , we group these outcomes into two classes , as in the example of the <WSD>die</WSD> , where we have arbitrarily constructed the classes `` ace '' and `` not ace '' . 
Meaning of the word marked with <WSD> tags:  a small cube with 1 to 6 spots on the six faces; used in gambling to generate random numbers