The present subjunctive can be thought of as a mood instead of as a tense. Tense refers to the time and a mood refers to the reaction of the speaker towards an action. It is often used to describe the experience with the world around you. The subjunctive mood is not something English speakers recognize immediately because it is very rarely used. The present subjunctive is based on the first-person singular (yo) form. It is formed by dropping the –o ending and adding the subjunctive endings. –Ar verbs use the endings of –er and –ir verbs, and the –er and –ir verbs use the endings or –ar. The first- person singular and the third-person singular are the same in the subjunctive form.

1. The subjunctive mood is generally used in sentences with a dependent clause. There must be an element in the main clause that requires the subjunctive in the dependent clause. Most of the sentences will have the same structure:
(main clause) + que + (second subject) + (dependent clause). A subjunctive cue must be in the main clause.
The subjunctive cue will belong to one of four categories. These categories are:
- doubt/negation
Dudar (doubt), negar (negate/deny), no creer (not to believe), no estar seguro (not to be sure), no es cierto/ no es verdad (it is not true), es dudoso (it is doubtful)
Dudo que vaya a regresar temprano. (I doubt that he/she will return early.)
- emotion
Temer/tener miedo (to fear/be afraid), estar contento/ triste etc. (to be happy/sad ect.), preocupar (worry), gustar (to like/please)
Estoy contento que llegues. (I am happy that you come.)
- opinion
Es importante (it’s important), es necesario (it’s necessary), es interesante (it’s interesting), es bueno/malo (it’s good/bad), es possible (It s possible), vale la pena (it’s worth it), importa (it matters)
Es Sorprendente que esté tan nublado. (It’s surprising that it is so cloudy.)
- command/request
Querer (to want), insistir (to insist), aconsejar (to advise), pedir (to ask), mandar (to order/command), sugerir (to suggest), rogar (to beg), exigir (to demand), recomendar (to recommend), decir (to tell). The verb Decir requires a subjunctive only when the sentence implies a request that somebody do something.
Mis amigos me dicen que arregle el asunto. (My friends tell me to fix the situation.)
2. The subjunctive mood is used to describe our opinions,feelings, and wishes towards the world around us. If we were to merely report information, we would have no use for the subjunctive. Because we are often reacting to the world around us though, we need the subjunctive mood in order to communicate in a more sophisticated manner in Spanish. When we merely report information in Spanish it may sound something like this: Mi madre esta en casa. (My mother is at home.)
The following is an example of the same sentence in the subjunctive mood: Es muy emocionante que mi madre esté en casa. (It is very exciting that my mother is at home.)
3. There is a group of expressions that always requires the use of the subjunctive mood:
- en caso de que (in case)
- sin que (without)
- con tal de que (provided that)
- antes de que (before)
- para que (so that)
- a menos que (unless)
4. There is another group of expression that require the subjunctive only at times. If the verb in the sentence is in future or command, then you use the subjunctive. The key is to ask yourself if the action has or hasn’t occured:
- mientras (while)
- cuando (when)
- después (after)
- en cuanto (as soon as)
- aunque (although/even though)
- tan pronto como (as soon as)
- a menos que (unless)