Future Past Tense

Future Past Tense    Simple Future                                         Future Idiomatic         Will                                                                   Going To     We can both use will and going to to make predictions  I think it will rain tomorrow  I think it is going to rain tomorrow We use will to make a rapid decision, a threat, an offer and a promise We use won't  to make or refuse something    We use going to to make a Prior Plan = the decision was made before the moment of speaking  We use going to to evidence signs = when there are signs that something is likely to happen    And Finally to compare                                                                               Are you busy this evening?  - I haven't made any plans                                                                                          I think I will probably watch TV  OR I think I'm probably going to watch Tv    Will and going to are both possible  in the example because we are "predicting" what will  happen because nothing is planned