Learn Spanish (Latin America): Los vendedores rodearon al turista.

This is the personal a in action. When the direct object of a sentence is a specific person, Spanish requires an a before it. Here, a combines with the masculine article el to form al.

Since turista ends in an a, how do we know it refers to a male tourist here?

Words ending in -ista (like turista, dentista, artista) are invariable, meaning the word itself doesn't change gender. We know this tourist is male because of the article el hidden inside the contraction al. If it were a female tourist, it would be a la turista.

It is tempting to spell the verb as rodiaron. Why is it rodearon?

The verb is rodear (to surround), an -ear verb, not an -iar verb. In fast spoken Spanish, the e in rodearon often glides and sounds like an i or a y to English ears, but you must keep the e when writing it.

How could we change this sentence to exclaim The amount of sellers that surrounded the tourist! using this lesson's structure?