El asesino escapó ayer.

El is the masculine singular definite article, meaning the.

In Spanish, common nouns usually need an article when they are the subject of a sentence, so El asesino is the normal way to say the killer / the murderer.

You would not normally say just Asesino escapó ayer in standard Spanish.

Asesino is the masculine form, and asesina is the feminine form.

So:

• el asesino = the male killer / murderer
• la asesina = the female killer / murderer

The form changes to match the gender of the person being described.

The accent mark shows where the stress goes and also helps identify the verb form.

• escapó = he/she/it escaped
• escapo = I escape

So the accent is important. In escapó, the stress is on the last syllable: es-ca-PÓ.

Without the accent, it would be understood as a different form.

Escapó is the preterite form of escapar, used for a completed action in the past.

Since the sentence includes ayer (yesterday), Spanish normally uses the preterite here because the escape is seen as a finished event:

• El asesino escapó ayer. = the escape happened and is completed.

This is different from the imperfect, which would suggest an ongoing, repeated, or background action.

Because escapó fits a single completed event better.

Compare:

• escapó = escaped / did escape
  A finished action.
• escapaba = was escaping / used to escape
  An ongoing, habitual, or background action.

With ayer, if you mean one specific escape that happened yesterday, escapó is the natural choice.

Yes. Spanish word order is fairly flexible.

These are all possible:

• El asesino escapó ayer.
• Ayer escapó el asesino.
• El asesino ayer escapó.

The version with ayer at the end is very natural and neutral. Moving ayer can change the emphasis slightly, but not the basic meaning.

Yes, and that is very common.

Both are possible:

• El asesino escapó ayer
• El asesino se escapó ayer

In many contexts, escaparse is especially common for escaping or getting away, so se escapó may sound a bit more idiomatic in everyday speech.

Still, escapó is perfectly correct.

Because el asesino is the subject of the sentence, not a direct object.

The personal a is used before specific human direct objects, for example:

• La policía vio al asesino. = The police saw the killer.

But here:

• El asesino escapó ayer.

El asesino is doing the action, so no personal a is used.

Yes, Spanish often drops subject pronouns and even subject nouns when the context is clear.

So Escapó ayer can mean:

• He escaped yesterday
• She escaped yesterday
• or, in context, The killer escaped yesterday

However, including El asesino makes the subject explicit and removes ambiguity.

A simple pronunciation guide is:

el ah-seh-SEE-no es-kah-PO ah-YER

A few key points:

• asesino is stressed on si: ah-seh-SEE-no
• escapó is stressed on the last syllable: es-kah-PO
• ayer is stressed on the second syllable: ah-YER

In Spain, the r in ayer is a light tap, not a strong English r.