How do I know when to use present indicative or present subjunctive?

Answer 1

The indicative mode is used to talk about facts that are certain, regardless of the verb tense. See the examples below: 

- I speak English - yo hablo inglés 

- He taught a lesson last week - él enseñó una lección la semana pasada

- We'll visit our grandma next Saturday - visitaremos a nuestra abuela el próximo sábado 

The subjunctive mode is used to describe how a person feels about a fact. It is mainly used to express a doubt, a wish, a hope, a recommendation, an emotion or an impersonal expression. See examples below: 

- Doubt: "Dudo que me llame", "No creo que me llamen" 

- Wish: "¡Quiero que ganes este partido!", "Deseo que me regale flores." 

- Hope: "Espero que te encuentres mejor.", "Espero que estés bien." 

- Recommendation: "Me recomendaron que estudiara dos horas al día." 

- Emotion: "Siento que estés enfadado conmigo.", "No me gusta que me digan lo que tengo que hacer." 

- Impersonal expression: "Es necesario que la gente vote en estas elecciones.", "Es importante que te tomes la medicación cada día." 

There are a few tips you can follow to help you determine when the subjunctive mode is being used. 

1. The subjunctive mode is commonly used in the second part of a complex sentence. A complex sentence has two subjects and two verbs, such as "Helena quería que Juan la llamara todas las noches." → “Elena” is the first subject and “quería” is the first verb (quería is in indicative mode since it is a certain fact). “Juan” is the second subject who does the action in subjunctive (llamara) since that action is what Elena wishes in the first part of the sentence.

2. The subjunctive mode is commonly found after a relative pronoun that acts as a connector, such as "Es importante que leas todos los días.” or “Hazlo como quieras.”

3. The subjunctive mode is often used in an expression that starts with the word "que", such as "¡Que tengas un buen día!" 

4. The subjunctive mode is used when explaining the purpose of an action using the words "para que". Example: "Le dimos dinero para que comprara comida para su familia." 

Have you found a pattern? - You are right; a verb in subjunctive mode will usually be introduced by the word "que"! 

An exception to that rule is expressing opinion. When expressing opinion, even if you use the word "que", you need to use the indicative mode. Example: "Creo que eso no es necesario" vs. "Dudo que eso sea necesario". The second sentence expresses doubt. That's why the verb "to be" is written in subjunctive mode (sea) instead of indicative mode (es) like when expressing an opinion. 

Verbo: SER 

Persona	Presente Indicativo	Presente Subjuntivo
Yo	Soy	Sea
Tú	Eres	Seas
Él / ella	Es	Sea
Nosotros/ nosotras	Somos	Seamos
Vosotros / vosotras	Sois	Seáis
Ellos / ellas	Son	Sean

Verbo: ESTAR 

Persona	Presente Indicativo	Presente Subjuntivo
Yo	Estoy	Esté
Tú	Estás	Estés
Él / ella	Está	Esté
Nosotros/ nosotras	Estamos	Estemos
Vosotros / vosotras	Estáis	Estéis
Ellos / ellas	Están	Estén

A trick you can use whenever you need to use subjunctive is to imagine somebody asks you to do something for them. Example:

Yo estoy contento → Ella quiere que yo esté contento

Nosotras somos amigas → Nuestros padres quieren que nosotras seamos amigas.

I hope this helps! :) 

Elisabet

Answer 2

You use the present indicative when the sentence does not express any doubt or uncertainty and the present subjunctive when the sentence does express doubt or uncertainty. Doubt or uncertainty is usually expressed with the word if in the sentence, which in Spanish is "si" without an accent on the letter i.

Let's try some example sentences and see the difference side by side:

If you have any questions, let me know. You have a question.

Si tengas unas preguntas, avísame. Tú tienes una pregunta.

If she wants to call me, I will be at home. She wants to call you.

Si ella quiera llamarme, estaré en casa. Ella quiere llamarte.

If it's serious then that's bad. It's serious.

Si sea grave luego no es bueno. Es grave.

Think about it like in the present subjunctive there are still more questions to ask. More doubts to clear up. In the present indicative we have the facts. Schedule a session with me if you'd like to understand more about this subject!