Los vecinos desfilan por la calle.

Los vecinos means the neighbors.

In Spanish, vecino / vecina usually refers to someone who lives nearby, especially in the same building, street, or area. Depending on context, it can also mean local residents.

• el vecino = the male neighbor
• la vecina = the female neighbor
• los vecinos = the neighbors / the residents

Spanish nouns change form depending on gender and number.

• vecinos is masculine plural
• vecinas is feminine plural

Los vecinos can refer to:

1. a group of men, or
2. a mixed group of men and women

If the group were all female, you would normally say las vecinas.

Because desfilan is the third-person plural present tense of desfilar.

The subject is los vecinos, which is plural, so the verb must also be plural.

Conjugation of desfilar in the present:

• yo desfilo
• tú desfilas
• él/ella desfila
• nosotros/nosotras desfilamos
• vosotros/vosotras desfiláis
• ellos/ellas desfilan

So Los vecinos desfilan = The neighbors parade / march.

Not exactly.

Desfilar usually means to parade, to march past, or to file along in an orderly way. It often suggests a procession, a line of people, or a formal/public movement.

So it is more specific than:

• caminar = to walk
• andar = to walk / go around
• pasear = to stroll
• marchar = to march

If the sentence uses desfilan, it suggests something more like a parade, procession, or organized movement rather than just ordinary walking.

Here, por means something like along, through, or down.

So desfilan por la calle means they are moving along the street or down the street.

This is a very common use of por for movement through a place.

Compare:

• por la calle = along/down the street
• por el parque = through the park
• por la ciudad = through the city

In Spanish, the definite article is used much more often than in English.

So Spanish often says:

• por la calle = along the street
• en la calle = in the street / on the street

Even when English might sound more natural without the in some cases, Spanish usually keeps the article.

Here, la does not necessarily mean one very specific street already known to the listener. It is just the normal Spanish way to say it.

Not if you want the same meaning.

• por la calle focuses on movement along the street
• en la calle focuses more on location in/on the street

So:

• Los vecinos desfilan por la calle = The neighbors are parading down the street.
• Los vecinos están en la calle = The neighbors are in the street.

With desfilar, por is the natural choice because the action involves movement.

The basic order here is very normal:

Los vecinos desfilan por la calle.

But Spanish word order is more flexible than English. You could also say:

Por la calle desfilan los vecinos.

That changes the emphasis slightly, putting attention first on where the action happens. It is still grammatical, but the original version is the most neutral and straightforward.

Not always.

In everyday Spanish, vecino can mean:

• a next-door neighbor
• someone living in the same building
• someone from the local area
• a resident of a town or neighborhood

So los vecinos might mean the neighbors in the narrow sense, or more broadly the local residents, depending on context.

Yes, but it sounds most natural if there is some kind of parade, procession, festival, or organized public event.

Because desfilar is more formal and specific than just walking, a native speaker would usually understand something like:

• a parade
• a religious procession
• a festival march
• people filing past in an orderly way

If you only mean that the neighbors are walking down the street normally, Spanish would more likely use caminan por la calle or van por la calle.