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Impersonal adjectives that call for the subjunctive

When you evaluate a situation in Portuguese using the phrase "it is" followed by an adjective and the word que, you are setting up a special grammatical environment. If the adjective expresses possibility, doubt, or necessity, the verb that follows que must be in the subjunctive mood.

English speakers often trip over this because English frequently uses the infinitive for these ideas ("It is important for you to go") or relies on standard verbs ("It is possible that it rains"). In Portuguese, adjectives like importante, possível, and necessário firmly demand the subjunctive when used in this specific structure.

Word list
importanteA1 important é importante que + subjunctive possívelA1 possible é possível que + subjunctive impossívelA2 impossible é impossível que + subjunctive improvávelA2 improbable é improvável que + subjunctive necessáriomA2 necessary é necessário que + subjunctive pouco provávelA2 improbable é pouco provável que + subjunctive precisomA2 necessary é preciso que + subjunctive desnecessáriomB1 unnecessary é desnecessário que + subjunctive duvidosomB1 doubtful é duvidoso que + subjunctive essencialB1 important é essencial que + subjunctive incertomB1 uncertain é incerto que + subjunctive provávelB1 probable é provável que + subjunctive urgenteB1 urgent é urgente que + subjunctive crucialB2 critical é crucial que + subjunctive indispensávelB2 indispensable é indispensável que + subjunctive viávelB2 feasible é viável que + subjunctive factívelC1 feasible é factível que + subjunctive imprescindívelC1 indispensable é imprescindível que + subjunctive inevitávelC1 inevitable é inevitável que + subjunctive obrigatóriomC1 mandatory é obrigatório que + subjunctive compulsóriomC2 mandatory é compulsório que + subjunctive
Possibility and doubt

Expressing whether something might or might not happen is a classic situation that calls for the subjunctive. When you use adjectives that convey doubt, uncertainty, or mere possibility, the outcome is not guaranteed. Words like possível, impossível, provável, and incerto all fall into this category and require the subjunctive in the part of the sentence that follows them.

É possível que eles cheguem amanhã.
(It is possible that they may arrive tomorrow.)
É duvidoso que o plano funcione.
(It is doubtful that the plan will work.)
É provável que chova à tarde.
(It is likely that it will rain in the afternoon.)
Necessity and importance

When you state that an action is needed, urgent, or essential, you are trying to influence reality. You are expressing what you want or need to happen, rather than describing something that has already occurred. This subjective push is another main pillar of the subjunctive mood. Common adjectives in this group include necessário, preciso, urgente, and obrigatório.

É importante que as crianças durmam bem.
(It is important that the children sleep well.)
É necessário que você assine o documento.
(It is necessary that you sign the document.)
É urgente que nós encontremos uma solução.
(It is urgent that we find a solution.)
É obrigatório que todos estejam presentes.
(It is mandatory that everyone be present.)
How to use them correctly

Two details can easily catch learners off guard. First, the impersonal adjective itself never changes gender or number. Because its subject is the entire phrase that follows, it remains in the masculine singular form. For example, you must say é necessário que a mulher fale, keeping the adjective masculine even though the person doing the action is female.

Second, if you are making a general statement and do not specify who needs to do the action, you drop the word que and use the infinitive instead of the subjunctive. For instance, é preciso estudar is a general rule, while é preciso que tu estudes applies specifically to you.

Finally, remember that adjectives expressing absolute certainty or obvious facts, such as óbvio or certo, do not call for the subjunctive. They take the standard indicative mood because they assert reality.

Summary

Whenever you use the structure é + adjective + que to express possibility, necessity, or doubt, the following verb must take the subjunctive mood. The adjective itself always stays in the masculine singular form.