For example;<br/>“Sarah will be happy in the party tonight.” (I’m sure Sarah will be happy.)<br/><br/>“Sarah would be happy in the party tonight.” (I’m not sure whether Sarah would be happy or not.) <br/><br/>As you can see, I used ‘will’ in certainty and ‘would’ in hypothetical without if-clauses.<br/><br/>It’s very kind of you to correct any ungrammatical phrases that I made throughout this question.