In Spanish the subjunctive is used:
♦ After impersonal expressions
Es necesario que compress el boleto hoy. It is necessary that you buy the ticket today.
The following expressions always trigger the subjunctive:
Es bueno - It is good.
Es importante - It is important.
Es imposible - It is impossible.
Es malo - It is bad.
Es mejor - It is better.
Es Necesario - It is necessary.
Es una lástima - It is a shame.
Es urgente - It is urgent.
♦ With verbs of “will and influence”
Yo quiero que tú digas al medico. - I want you to speak to the doctor.
With verbs of “emotion.”
Me gusta que tengas una actitud positiva. - I’m glad you have a positive attitude.
♦ With verbs of “doubt or denial.”
No creo que Mauricio quiera ir al medico. I don’t believe Mauircio wishes to go to the doctor
♦ In subordinate adjective clauses where the antecedent is not certain
Necesito un libro que tenga artículos sobre nutrición. I need a book that has articles on nutrition.
♦ Following adverbial clauses
Hay unas vendas en el botoquín en caso de que las necesites. There are some bandages in the first-aid kit in case you need them.
Note: The following Spanish conjunctions always require the subjunctive:
a menos que - unless
antes (de) que - before
en caso (de) que - in case
para que - so that
sin que - without, unless