Impersonal Expressions and the Subjunctive
When you make general statements of opinion, probability, or emotion, you will often use impersonal expressions. These are phrases that start with é (it is) and do not refer to a specific person.
In Portuguese, when an impersonal expression is followed by the word que (that), the following verb is usually conjugated in the Present Subjunctive (o presente do conjuntivo).
Value Judgments
Use the subjunctive after expressions that state a strong opinion or value judgment, such as é essencial que (it is essential that), é importante que (it is important that), or é bom que (it is good that).
Probability and Possibility
Expressions that convey uncertainty or likelihood rather than objective facts also trigger the subjunctive. Common examples include é provável que (it is likely that) and é possível que (it is possible that).
Expressing Regret
When an impersonal expression conveys an emotional reaction, like sadness or regret, the subjunctive is required. A very common phrase for this is é uma pena que or é pena que (it's a pity/shame that).
Negative Sentences
If the subjunctive clause is negative, simply place the negative word (like não) directly before the subjunctive verb.