What is the basic sentence structure of a subjunctive Sentence?
present tense + que + present subjunctive
How is the subjunctive mood used vs the indicative?
Subjunctive: used in a way that relates to how the speaker FEELS about something, or believed reality. (i.e. expresses doubt, feelings, wish, intent, or command) toward a possible action/state of being
Indicative: states what is real, facts, and declarations
Quiero que no tengas frío.
(I want you to be not cold.) It's irrelevant whether the person is cold or not. The sentence expresses a wish, not reality.
Siento que tengas frío.
I'm sorry you're cold.) The sentence expresses the speaker's emotions about a perceived reality. What is important in this sentence is the speaker's feelings, not whether the other person is cold.
Te doy mi chaqueta para que no tengas frío.
I'm giving you my coat so you won't be cold. The sentence expresses the speaker's intent, not necessarily reality.
Se permite que lleven chaquetas allí.
(People are allowed to wear jackets there.) The phrase expresses permission for an action to take place.
Di a ella que lleve una chaqueta.
(Tell her to wear her jacket.) Expresses a command or wish of the speaker.
No hay nadie que tenga frío.
(Nobody is cold.) Expression of negationof the action in a subordinate clause.
Tal vez tenga frío
(Perhaps he is cold.) This is an expression of doubt.
Si yo fuera un rico, tocaría el violín.
(If I were a rich man, I would play the fiddle.) This is an expression of a statement contrary to fact.
Es imposible que salga tarde.
Es probable que salga tarde.
It is impossible that it is leaving late.
It is likely that it will leave late.
Busco un carro barato que funcione.
(I'm looking for a cheap car that works.)
No creo que sea ella
(I don't believe it's she.)
The subjunctive is used in this example because the subordinate clause is negated by the main clause. Generally, the indicative is used with creer que or pensar que, (Creo que es ella) while the subjunctive is used with no creer que or no pensar que.
Indicative: Es obvio que tienes dinero. (It is obvious you have money.)
Subjunctive: Es bueno que tengas dinero. (It is good you have money.)
Indicative: Habla bien porque es experto. (He speaks well because he's an expert.)
Subjunctive: Habla como si fuera experto. (He speaks as if he were expert.)
Indicative: Quizás lo pueden hacer. (Perhaps they can do it (and I'm sure of it.))
Subjunctive: Quizás lo puedan hacer. (Perhaps they can do it (but I doubt it.))
Indicative: Hay políticos que tienen coraje. (There are politicians who have courage.)
Subjunctive: ¿Hay políticos que tengan coraje? (Are there politicians with courage?)
Indicative: Llegaré aunque mi carro no funciona. (I will arrive even though my car isn't running.)
Subjunctive: Llegaré aunque mi carro no funcione. (I will arrive even if my car isn't running.)