"Mood. Verbs have 1 to 3 moods: (1) the indicative (the most common; used for ordinary objective statements), (2) the impermative (used for responding or comanding), and (3) the subjunctive.    
   Subjunctive verbs cause the most difficulty; they are used to primarily for expressing a wish. ... The subjunctive is sometimes used uncorrectly, eg, where matters of fact—not supposition—are discussed."


AMA Manual of Style: 10th Edition