What the subjunctive changes about a Spanish sentence

With está aquí I say that someone is here. With me alegra que esté aquí I say that I am glad they are here. The person can be present in both cases. The event is not imaginary because of the change to esté.

This is an important starting point for understanding the subjunctive. It is a grammatical choice used in several kinds of construction. Spanish has no special category for things that are false or unreal.

What the speaker is presenting

In a sentence such as Quiero que venga, the coming is something wanted. In Dudo que venga, it is something doubted. In Me alegra que haya venido, the speaker reacts to someone having come.

You establish that relationship from the surrounding expression, and the verb form is part of it. If you look only for uncertainty, you will explain some examples and get others wrong.

“Not asserted” can be a useful description in some analyses, but it must not be confused with “not true”. In a sentence, a speaker can take an event for granted and comment on it rather than introduce it as new information.

A person you know or a requirement to fill

Compare these two sentences:

Spanish	A natural reading
Conozco a alguien que habla japonés.	I know a person who speaks Japanese.
Necesito a alguien que hable japonés.	I need someone who speaks Japanese.

With the second, the speaker describes a requirement without identifying a particular person who meets it. The speaker does not claim that no such person exists. With the first, the speaker describes someone they know.

This is a useful reason to pay attention to mood when reading: it can change how a description relates to the person or thing being discussed.

A future event can be expected

Cuando termine la reunión, te llamo is about a call after the meeting ends. The speaker may fully expect the meeting to end. The subjunctive in the time clause is not a probability score.

Compare a routine: Cuando termina la reunión, todos vuelven a sus oficinas. The indicative fits the habitual account. The relationship expressed by the clause matters alongside the time reference.

For an introduction to common constructions, see four useful subjunctive patterns.

English expresses these meanings too

English speakers use their own combination of verb forms, other words and sentence structures to express wishes, uncertainty and reactions. It also has productive subjunctive uses, such as “The committee recommended that she be appointed”. Here, be expresses the recommended appointment without changing to is or was.

Speakers of the two languages do not divide all these jobs in the same way. That is a difference in grammar. It is no sign of how well either group of speakers understands reality or uncertainty.

Read beyond the verb ending

When you encounter a subjunctive form, identify the expression around it. Is someone making a request, reacting to a known event, describing a requirement or anticipating a later action?

Try changing the construction and checking what changes in the meaning. Not every change permits both moods, and for some contrasts you need context. Those constraints are explained in a grammar reference.

The aim is to understand the sentence being used. When a clear example does not fit a memorable explanation, go with the example.