Estoy asustado.

Because asustado describes a state or condition in this sentence, not a permanent characteristic.

• estar = to be, for temporary states/conditions
• ser = to be, for identity, origin, profession, and more permanent descriptions

So:

• Estoy asustado = I am scared
• Soy asustado would sound like I am a scared/fearful person by nature, which is not what people usually mean.

Asustado is a past participle used like an adjective here. It means frightened, scared, or afraid.

It agrees with the person it describes:

• Estoy asustado = said by a male speaker
• Estoy asustada = said by a female speaker

So even though it comes from the verb asustar (to frighten / to scare), in this sentence it is functioning as an adjective.

No. In Spanish, the subject pronoun is often omitted because the verb already shows who the subject is.

• Estoy asustado = I am scared
• Yo estoy asustado = also correct, but yo adds emphasis or contrast

For example:

• Estoy asustado = neutral
• Yo estoy asustado, pero ella no = I’m scared, but she isn’t

So in most situations, Estoy asustado is the most natural version.

Because adjectives in Spanish usually agree in gender and number with the person they describe.

Examples:

• Estoy asustado = male speaker
• Estoy asustada = female speaker
• Estamos asustados = a group of males or a mixed group
• Estamos asustadas = a group of females

This agreement is very common in Spanish.

They are very similar, but not always identical.

• Estoy asustado = I am scared / frightened
• Tengo miedo = I am afraid / I feel fear

In many situations, both work:

• Estoy asustado because of the noise.
• Tengo miedo because of the noise.

A useful difference:

• asustado often suggests you have been frightened by something
• tener miedo can sound broader and may describe fear in general

So both are common, but Estoy asustado can feel a bit more like I’ve been scared or I’m in a frightened state.

A simple pronunciation guide is:

es-TOY ah-soos-TAH-doh

A few details:

• estoy: stress on the second syllable, -toy
• asustado: stress on ta
• the d in -ado is usually softer than English d
• Spanish vowels are short and clear:
  • e as in bed but cleaner
  • o as a pure oh
  • a as in father
  • u as in rule, but shorter

In Spain, the pronunciation is essentially the same here.

Usually it means scared or frightened, not just surprised.

If you want surprised, Spanish more commonly uses:

• sorprendido = surprised

So:

• Estoy asustado = I’m scared
• Estoy sorprendido = I’m surprised

Sometimes fear and surprise happen together, but asustado clearly points to fear.

It comes from the verb asustar, which means to scare or to frighten.

Examples:

• Eso me asusta = That scares me
• Me has asustado = You scared me
• Estoy asustado = I am scared

So the sentence is built with:

• estoy = first person singular of estar
• asustado = past participle/adjective from asustar

In standard Spanish, especially in writing, you should say Estoy asustado.

You may sometimes hear something like asustao in very informal speech, because the d in -ado can be weakened or dropped in some accents. But:

• asustado = standard, correct form
• asustao = colloquial pronunciation/spelling imitation, not appropriate for normal learners to use in standard writing

So for learning Spanish, stick with Estoy asustado.

Very simply:

• No estoy asustado = I’m not scared
• ¿Estoy asustado? = Am I scared?

You can also use intonation in speech to show it is a question.

Other examples:

• ¿Estás asustado? = Are you scared?
• No estamos asustados = We aren’t scared

Yes, that is exactly how it is normally used.

Estoy asustado usually means:

• I feel scared right now
• I am in a frightened state at the moment
• something has made me feel afraid

That is why estar is used. It fits temporary emotional or physical states very well.

Yes, usually.

• nervioso = nervous
• asustado = scared/frightened

So if someone says Estoy asustado, it normally suggests more fear than Estoy nervioso.

Compare:

• Estoy nervioso antes del examen = I’m nervous before the exam
• Estoy asustado por el ruido = I’m scared because of the noise

So asustado is generally the stronger emotion.