é possível que + Subjunctive

The structure é possível que is an impersonal expression. This means it doesn't have a specific person as a subject (like 'I' or 'You'); it simply evaluates a situation.

1. The Subjunctive Trigger:
Whenever you use this expression, the verb that follows the word que must be in the subjunctive. To form the present subjunctive, start with the 1st person singular (eu) form of the present indicative, drop the -o, and add the opposite vowel endings:

• For -ar verbs, the vowel changes to -e (e.g., falar -> falo -> fale).
• For -er and -ir verbs, the vowel changes to -a (e.g., comer -> como -> coma).
• This rule applies perfectly to many irregular verbs too (e.g., fazer -> faço -> faça). Only seven verbs are completely irregular: ser (seja), estar (esteja), dar (dê), ir (vá), saber (saiba), querer (queira), and haver (haja).
• To maintain pronunciation, verbs ending in -car, -gar, and -çar require mandatory spelling changes: -car becomes -que (ficar -> fique), -gar becomes -gue (chegar -> chegue), and -çar becomes -ce (começar -> comece).

2. Tense Usage:

• Use the Present Subjunctive for possibilities in the present or future.
• Use the Pretérito Perfeito do Subjuntivo for possibilities regarding the past (e.g., 'It's possible he already left').
• If the main clause is in the past (Era possível que...), the following verb shifts to the Imperfect Subjunctive (e.g., Era possível que chovesse).
• If the possibility refers to an action already completed before that past moment, use the Mais-Que-Perfeito do Subjuntivo (e.g., Era possível que ele já tivesse saído).

3. The Infinitive Alternative:
You can drop the word que and use an infinitive instead. If making a general statement without a specific subject, use the impersonal infinitive (e.g., É possível chegar cedo). If there is a specific subject, you can use the Personal Infinitive (e.g., É possível eles chegarem cedo).

4. Pronoun Placement:
The word que is a strong attractor. This means any object or reflexive pronouns must be placed before the verb (proclisis), e.g., É possível que ele se atrase (never atrase-se).

5. Register:
This is a standard expression used in both Brazil and Portugal. The subjunctive is absolutely mandatory after é possível que; using the indicative here is a grammatical error.

6. The Negative Form:
The negative form, não é possível que, follows the exact same subjunctive rules. It is extremely common in everyday Portuguese to express shock, disbelief, or frustration (similar to 'I can't believe that...' or 'It's impossible that...').