estoy

In a sentence

• Estoy feliz porque es un día soleado.

  I am happy because it's a sunny day.

  Here 'estoy' indicates a temporary state or feeling, expressing how the speaker currently feels.

• Estoy en la biblioteca estudiando.

  I am in the library studying.

  In this context, 'estoy' is used to indicate the person's current location and activity, emphasizing presence and action.

• Estoy escribiendo una carta a mi amiga.

  I am writing a letter to my friend.

  Here, 'estoy' is used as part of the present progressive tense, showing an action happening at this moment.