Subjunctive Mood

The uses of the subjunctive may be divided into two major categories:  the independent uses of the subjunctive and the dependent uses. All the dependent uses of the subjunctive arise from the independent uses.  However, throughout its history, the subjunctive came to be used more and more as a grammatical marker of subordination.   That is, Late Latin speakers would use it in any subordinate clause.  Hence, its name:  subjunctive = the mood for "subjoining" a subordinate clause to the main verb.