Los campesinos de ese pueblo están orgullosos de su trabajo en el campo.

In Spanish, you almost always use an article (like el, la, los, las) before a noun, even when speaking generally about a group.

• Los campesinos de ese pueblo…
  = The peasants / farm workers from that town…

If you said just “Campesinos de ese pueblo están orgullosos…”, it would sound incomplete or ungrammatical in standard Spanish.

So:

• Los campesinos trabajan mucho.
  = Farm workers work hard. (general statement)

The definite article “los” helps mark the group you’re talking about, often used for whole categories or groups of people.

Campesino literally means someone from el campo (the countryside), but it usually refers to:

• small-scale farmers
• rural farm workers or peasants
• people living and working in the countryside, often with modest means

In many parts of Latin America, campesino can have social and cultural connotations: it can be a neutral or even positive identity word, but depending on tone/context, it can also sound class-based (like peasant).

Compare:

• campesino – rural worker / small farmer / peasant
• granjero – farmer (more like the owner or manager of a farm; used less frequently in some Latin American regions)

So “Los campesinos de ese pueblo” is closer in feel to “The farm workers / peasant farmers from that village” than to big, industrial “farmers.”

Both could exist, but they mean different things:

• de ese pueblo = from that town / belonging to that town
  • Focus on origin or community.
• en ese pueblo = in that town
  • Focus on location.

“Los campesinos de ese pueblo…” emphasizes that these campesinos are the ones who come from / belong to that village.

If you said:

• Los campesinos en ese pueblo están orgullosos…
  you’d be saying: The campesinos who are (currently) in that village are proud… (maybe they’re from somewhere else but are there now).

This is the classic ser vs. estar contrast.

• estar orgulloso = to be proud (of something specific, usually justified, often more temporary or situational)
• ser orgulloso = to be (a) proud person (as a character trait; often “proud” in the sense of arrogant / haughty)

So:

• Están orgullosos de su trabajo.
  = They feel proud of their work. (normal, positive)

• Son orgullosos.
  = They are proud people / arrogant. (personality description, often negative)

In this sentence, we want the normal, justified feeling of pride, so estar is used.

Orgullosos must agree with campesinos in:

• number (singular/plural)
• gender (masculine/feminine)

Here:

• campesinos = masculine plural
  → adjective: orgullosos (masculine plural)

If you change the subject, the adjective changes:

• El campesino está orgulloso. (one male)
• La campesina está orgullosa. (one female)
• Las campesinas están orgullosas. (group of women)

If the group is mixed (men + women), Spanish grammar defaults to masculine plural:

• Los campesinos están orgullosos.
  (could be all men or mixed group)

With “orgulloso”, the most natural and common preposition is de:

• estar orgulloso de algo / de alguien
  = to be proud of something / someone

So:

• Están orgullosos de su trabajo.
  = They are proud of their work.

“Orgulloso por” can appear, but it’s much less common and often sounds off or overly specific. In standard usage, learners should strongly prefer:

• orgulloso de
  • noun / pronoun / infinitive
    e.g. orgullosos de sus hijos, orgullosas de haber participado

Su in Spanish is ambiguous:

• su trabajo can mean:
  • his work
  • her work
  • their work
  • your work (formal usted / ustedes)

In this sentence, the subject is “Los campesinos de ese pueblo” (they), so “su trabajo” naturally reads as:

• their work

If we needed to be extra clear, we could rephrase:

• el trabajo de ellos = their work (of them)
• el trabajo de él / de ella = his / her work

But in normal context, su trabajo is enough and is understood from the subject.

El campo is context-dependent. Common meanings:

1. the countryside / rural areas
   
   • Me gusta vivir en el campo. = I like living in the countryside.
2. the fields / farmland
   
   • Trabaja en el campo. = He works in the fields.

In your sentence with campesinos, both ideas overlap:

• su trabajo en el campo = their rural, agricultural work in the countryside/fields.

It clearly doesn’t mean something like “field” as in field of study or sports field here. Those would need extra words:

• el campo de fútbol – soccer field
• el campo de la medicina – the field of medicine

Yes, pueblo is not the same as city.

• pueblo – a town, village, or small community (usually smaller and more rural)
• ciudad – a city (larger, more urban)

So:

• ese pueblo – that town / that village

In Latin America, pueblo also has a cultural nuance: “the people” as a community, especially working-class or rural people:

• la voz del pueblo – the voice of the people

Here, though, it’s just the literal town/village the campesinos are from.

In Spanish, trabajo can mean both:

• work as an uncountable concept (like English “work”)
• a job or a piece of work

In “su trabajo en el campo”, it’s being used like “their work” in general, not individual tasks or jobs:

• Están orgullosos de su trabajo en el campo.
  = They’re proud of their work (collectively, what they do for a living).

If you said:

• Sus trabajos en el campo
  you’d be emphasizing separate jobs or different kinds of work each one does, which is not needed here.

That sounds wrong/natural to a native speaker.

Two problems:

1. ser orgulloso describes a character trait: they are proud/arrogant people.
2. With ser orgulloso, the preposition de is not the usual pattern in the same way as with estar orgulloso de.

To express normal, positive pride about their work, you should say:

• Los campesinos de ese pueblo están orgullosos de su trabajo en el campo.

If you really wanted to use ser, it would usually mean:

• Los campesinos de ese pueblo son muy orgullosos.
  = They are very proud (as a personality trait; can imply stubborn / haughty).

The choice between este / ese / aquel shows distance (physical, mental, or conversational):

• este = this (near the speaker)
• ese = that (near the listener, or just not near the speaker)
• aquel = that over there (far from both; or more distant in time/idea)

So “ese pueblo” could mean:

• that town we’re talking about (not right here)
• that town near you
• that town we both know, but not close to me

You could say:

• este pueblo – this town (here, where I am)
• aquel pueblo – that town over there / that (more distant) town

The sentence just chooses ese, a common neutral “that.”