When would one use the subjunctive form of a verb?

Question

I'm trying to recall some high school spanish and having difficulties as its been several years.

Under what conditions would one use the subjunctive form of a verb? Why would you want to use it to express something?

Answer 1

This can be a very involved topic, and it would take pages to discuss all the nuances (see any Spanish grammar book). But the basic idea, as Wikipedia puts it, is:

The subjunctive of a verb is used to express certain connotations in sentences such as a wish or desire, a demand, an emotion, uncertainty, or doubt.

The subjunctive is technically a grammatical mood that can be contrasted with the indicative mood. The indicative mood is associated with statements of fact or certainty, while the subjunctive covers statements of doubt or desire. However, there are cases where this general rule of thumb doesn't seem to apply, and those can come down to just memorizing rules.

One resource online reviews the subjunctive by splitting it into the following cases:

1. In independent clauses:
   1. Expressing deference or respect (with poder, querer, or deber)
   2. With words meaning "maybe" or "perhaps" (e.g. quizá(s), tal vez)
   3. In imperatives based on the subjunctive
2. In noun clauses following verbs of influence, doubt or denial, emotion, or subjective reactions
3. In adverbial clauses where the cause is anticipated (e.g. para que, cuando, después de que)
4. In adjectival clauses where the modified word is negated, nonexistent, or indefinite
5. After como si
6. In "if" clauses involving an "unreal" condition

For more details, it might be helpful to ask a more specific question about a particular aspect of the subjunctive.