How do I know when to use the present subjunctive?

Answer 1

There are three necessary components needed to trigger the subjunctive:

1. A clause with a verb that indicates subjunctive, like a WEIRDO verb (Wishes, Emotions, Impersonal expressions, Recommendation, Doubt/Desire and Ojalá)
2. The connecting word "que"
3. If there is NO "que", then the second verb in the sentence simply stays in its unconjugated form. For example: Espero vivir en una casa grande
4. Following the que, there must also be a change of subject.

For example, the sentence "Quiero que mi mama me compre un coche nuevo" (I want my mom to buy me a new car) triggers the subjunctive because it contains all three necessary components. "Querer" is a WEIRDO verb as it falls under the category of Wishes. There is the linking "que" and it is followed by a change of subject, mi mama.

As for the word "ojalá", it will always trigger the subjunctive and is typically omitted from the sentence. That's why the phrase "Have a good day!" begins solely with "¡Que tenga un buen día!" because ojalá is simply implied. I hope this helps!

Answer 2

The present subjunctive is used when something is not necessarily fact. For example, If you are unsure of something you would use the subjunctive: “dudo que vayas a la playa,” meaning, I doubt that you go to the beach. The subjunctive is used here because there is doubt in the situation.

It is also used when wishing something (Que tengas suerte = good luck!), when giving advice (sugiero que subjunctive) or when demanding something.