The subjunctive mood is a grammatical mood used to express wishes, hypothetical situations, or actions that are not certain to occur. It often appears in sentences that convey desires, suggestions, or conditions contrary to fact. For example, in English, one might say, "I wish he were here," where "were" indicates a situation that is not real. In many languages, including Spanish and French, the subjunctive mood has specific verb forms that differ from the indicative mood, which states facts. Understanding the subjunctive is essential for mastering these languages, as it helps convey nuances in meaning and intention.