Learn Hardcore Spanish (Spain): Los domingos la calle se hace peatonal para el mercado. - On Sundays the street becomes pedestrian-only for the market.

Los domingos means on Sundays as a habitual action (every Sunday).
El domingo usually refers to one specific Sunday (this/next/last Sunday).
En los domingos is not idiomatic in this sense; Spanish normally uses the article alone for days to mean on. Use los domingos, not en los domingos.

Can I move los domingos to the end: La calle se hace peatonal los domingos?

Yes. Both orders are natural. Placing Los domingos first emphasizes the time frame; placing it at the end is more neutral or end-weighted.

Should there be a comma after Los domingos?

It’s optional. Many writers would add one after an initial time phrase: Los domingos, la calle… Without the comma is also common in short, clear sentences.

What exactly is se hace peatonal? Is se reflexive or passive here?

Most naturally, it’s pronominal hacerse + adjective = become: the street becomes pedestrian-only.
There is also a possible passive-like reading with se (pasiva refleja) if you say Se hace peatonal la calle = the street is made pedestrian. In your word order (La calle se hace peatonal), readers usually understand a change of state: becomes.

Why not just say La calle es peatonal?

Es peatonal suggests a permanent characteristic. The sentence is about a change/state that happens on Sundays, so se hace peatonal (becomes) fits better.
Note: está peatonal is not idiomatic; you’d say está cerrada al tráfico if you need a temporary state with estar.

Could I use other verbs like convertirse, volverse, or a more formal option?

Se convierte en una zona peatonal (becomes a pedestrian area) — formal/explicit.
Pasa a ser peatonal — neutral.
Se peatonaliza — bureaucratic/municipal register (from the verb peatonalizar).
Everyday alternative: Se cierra al tráfico.

Why is it para el mercado and not por el mercado?

Para expresses purpose: it becomes pedestrian in order to hold the market.
Por would express cause: because of the market. You may hear por el mercado in speech, but para el mercado clearly signals the intended purpose.

Why do we use the article in para el mercado? Why not drop it?

Spanish generally requires the article with a known, specific event. Here it’s the weekly market everyone in context knows about, so el mercado is natural. Para mercado (without article) sounds wrong.

How does the adjective peatonal behave? Does it agree?

It agrees in number, not gender form: la calle es peatonal; las calles son peatonales.
Common collocations: calle peatonal, zona peatonal.

Is peatonil also correct?

Yes. Peatonal and peatonil are both accepted adjectives. In Spain, peatonal is more frequent; peatonil can sound a bit more formal or technical.

What’s the gender of calle and mercado?

Calle is feminine: la calle, esta calle.
Mercado is masculine: el mercado, este mercado.

Can I drop the article and say Domingos la calle…?

Not in standard usage. Use Los domingos…. Omitting the article is mostly seen in headlines or signage.

What about Todos los domingos or Cada domingo?

Both are fine and slightly stronger than los domingos:

Todos los domingos = every single Sunday (no exceptions implied).
Cada domingo = each Sunday (very similar meaning).
Los domingos = on Sundays (habitually), without stressing completeness.

Could I say durante el mercado instead of para el mercado?

Yes, but it changes the nuance:

Para el mercado = for the purpose of the market.
Durante el mercado = during the time the market is happening. Both can be true; choose based on what you want to highlight.

If there are several streets, how does the sentence change?

Pluralize verb and adjective: Los domingos las calles se hacen peatonales para el mercado.

How is the pronunciation in Spain for key words?

hace: the h is silent; c before e is pronounced like English th in think: [ˈaθe].
calle: yeísmo is common, so ll sounds like y: [ˈkaʝe].
peatonal: stress on the last syllable: pea-to-nal.

Is mercado the best word for a Sunday street market in Spain?

It works, but you’ll also hear:

mercadillo (typical street/flea market)
rastro (in some cities, e.g., Madrid’s famous Rastro)
Choose based on local usage: para el mercadillo is very natural in many towns.