Decidió dimitir hoy.

Decidió is the preterite (in Spanish grammar, pretérito indefinido) of decidir.

It is third person singular, so it can mean:

• he decided
• she decided
• you decided in the formal singular (usted)

The preterite shows the decision as a completed action in the past.

Spanish often omits subject pronouns because the verb ending already tells you who the subject is.

So decidió already signals él / ella / usted.
If the speaker wants to be explicit or add emphasis, they can say:

Él decidió dimitir hoy.
Ella decidió dimitir hoy.

But very often, Spanish leaves that pronoun out.

After decidir, Spanish commonly uses an infinitive to express what someone decided to do.

So the pattern is:

decidir + infinitive

Examples:

• Decidió dimitir.
• Decidieron esperar.
• He decidido cambiar de trabajo.

This is the Spanish equivalent of English decide to + verb.

Because decidir normally goes directly with the infinitive:

decidir + infinitive

So:

• Decidió dimitir = correct
• Decidió a dimitir = not correct

This is a good example of how English to before a verb does not automatically translate as Spanish a.

There is a different structure, decidirse a + infinitive, which means something like to make up one’s mind to:

• Se decidió a dimitir.

But that is a different construction from plain decidir + infinitive.

In Spain, dimitir is a very common verb meaning to resign, especially from:

• a political post
• an official position
• a role of responsibility

So it is especially common in news and formal contexts:

• El ministro dimitió.
• La alcaldesa decidió dimitir.

For an ordinary job, Spanish may also use other expressions depending on the situation, but dimitir is especially natural for stepping down from a position.

Sometimes, but not always.

Dimitir is especially used for resigning from a post or office.
Renunciar is broader and often means to give up, to renounce, or to resign from something, often with a:

• Renunció al cargo.
• Renunció a sus derechos.

So in many Spain contexts:

• Decidió dimitir hoy sounds very natural for He/She decided to resign today
• Decidió renunciar al cargo hoy is also possible, but the structure is different

So they can overlap, but they are not always interchangeable word for word.

Yes, it can go somewhere else. Spanish word order is flexible.

All of these are possible:

• Decidió dimitir hoy.
• Hoy decidió dimitir.
• Decidió hoy dimitir.

The version with hoy at the end is very natural and neutral. Putting hoy at the beginning often gives it a little more emphasis:

• Hoy decidió dimitir. = It was today that he/she decided to resign

So the position can change depending on rhythm, emphasis, and style.

The accent mark shows the stress goes on the last syllable:

de-ci-dió

Without the accent mark, Spanish spelling rules would suggest a different stress pattern.

This accent is also part of a very common preterite ending:

• habló
• comió
• decidió

So the accent is not optional here. It is the correct spelling of the third person singular preterite.

Yes, very often.

In much of Spain, when the time expression is connected to the current time period such as hoy, speakers frequently prefer the present perfect:

• Hoy ha decidido dimitir.
• Ha decidido dimitir hoy.

This is very common in Peninsular Spanish.

Decidió dimitir hoy is still understandable and can be used, but if you want a very typical everyday Spain pattern, ha decidido is often the more natural choice with hoy.

A simple way to remember it for Spain Spanish is:

• hoy, esta mañana, esta semana, este año often go well with he/ha + participle

Not necessarily.

Dimitir can be used on its own if the context already makes clear what position the person is leaving:

• Decidió dimitir hoy.

If you want to specify the role, you can add it:

• Decidió dimitir de su cargo hoy.
• Decidió dimitir de la presidencia.

So the shorter sentence is perfectly normal when the listener already knows what the person is resigning from.