Learn Hardcore Indonesian: Kami berjalan di lapangan yang terasa luas malam ini. - We walk on the field that feels spacious tonight.

So kami berjalan… means we walked… but the listener was not part of that group.
If the speaker wants to include the listener (e.g. “We are walking tonight, you and I”), they would say kita berjalan… instead.

How do we know if berjalan means “walked” (past) or “are walking” (present) when the verb doesn’t change?

Indonesian verbs don’t show tense the way English verbs do. Berjalan by itself just means to walk / walking.
The time is understood from context words like malam ini (tonight), kemarin (yesterday), sedang (currently), etc.
In English you might translate this sentence as:

We are walking in the field that feels spacious tonight. (ongoing action)
We walked in the field that felt spacious tonight. (completed action earlier this evening)

Both are possible; the exact tense depends on the broader context, not on berjalan itself.

What exactly does berjalan mean here? Is it always “to walk on foot”?

In this sentence, berjalan means to walk (on foot).
More generally, berjalan can also mean to run / to function for things like programs or machines, e.g. Program ini berjalan dengan baik (This program runs/works well).
If you want to make it very clear that you mean “on foot”, you can also say berjalan kaki, but in Kami berjalan di lapangan… the “on foot” meaning is already clear from context.

Why is the preposition di used in di lapangan and not ke lapangan?

di means in/at/on (location).
ke means to (direction / movement towards).

Kami berjalan di lapangan means We walked in/at the field (your movement happens within that place).
If you say Kami berjalan ke lapangan, it means We walked to the field (your movement is heading towards the field, not necessarily within it).
So di lapangan emphasizes being located in the field while walking.

What is the role of yang in lapangan yang terasa luas?

Yang introduces a descriptive clause, similar to that / which / who in English relative clauses.
Lapangan yang terasa luas literally means the field that feels spacious.
So yang terasa luas is a little “mini-sentence” describing lapangan.
Without yang, the structure and meaning would change (see next question).

Could we say lapangan terasa luas without yang? What’s the difference from lapangan yang terasa luas?

Yes, but the structure changes:

Lapangan terasa luas.
= The field feels spacious.
Here lapangan is the subject of a full sentence, and terasa luas is the predicate.
lapangan yang terasa luas
= the field that feels spacious
This is a noun phrase: lapangan is the noun, and yang terasa luas is an adjective-like clause attached to it.

In your original sentence, lapangan yang terasa luas is part of a larger sentence, so it’s used as a noun phrase, not as a stand‑alone sentence.

What does terasa mean exactly? How is it different from merasa?

Both come from the root rasa (feeling, taste, sense):

terasa = to be felt / to feel (to someone)
It describes how something seems/feels:
- Lapangan ini terasa luas. = This field feels spacious.
- Hari ini terasa singkat. = Today feels short.
merasa = to feel (someone actively feels something):
- Saya merasa sedih. = I feel sad.
- Saya merasa lelah. = I feel tired.

So lapangan yang terasa luas is “the field that feels spacious,” focusing on how the field is perceived.

Does luas here mean “wide” or “big”? What nuance does it have?

Luas is usually translated as wide, broad, spacious, extensive.
For a field, it suggests a large open area with a lot of space, not cramped or small.
Depending on context, English equivalents might be:

spacious field
wide field
large open field

The idea is more about spread-out / plenty of space rather than just “big” in a general sense.

Can malam ini modify luas? Does it mean “the field feels more spacious tonight”?

As written, malam ini most naturally modifies the whole event:
Kami berjalan … malam ini = We walked / are walking … tonight.

However, semantically it can also be understood as:

the field (particularly) feels spacious tonight.

If you want to emphasize that it’s tonight that it feels especially spacious, you could say:

Lapangan ini terasa lebih luas malam ini.
= The field feels bigger/more spacious tonight.

In your sentence, the timing of the walk and the feeling of spaciousness both naturally fall under malam ini.

Is the word order fixed? Could we move malam ini earlier, like Kami berjalan malam ini di lapangan yang terasa luas?

Indonesian word order is fairly flexible for time and place expressions.
These are all grammatical:

Kami berjalan di lapangan yang terasa luas malam ini.
Kami berjalan malam ini di lapangan yang terasa luas.
Malam ini kami berjalan di lapangan yang terasa luas.

The differences are about emphasis:

Putting Malam ini at the start highlights tonight.
Keeping it at the end feels more neutral and natural in many contexts.

Why is there no plural marker? How do we know if lapangan is “field” or “fields”?

Indonesian often does not mark singular vs plural explicitly; it’s understood from context.
Lapangan can mean field or fields depending on the situation.
If you want to make it clearly plural, you can say:

lapangan-lapangan (reduplicated form – “fields” in general)
beberapa lapangan (several fields)

In your sentence, di lapangan yang terasa luas is most naturally understood as a single field, but context could allow “fields” too.

Is kami formal, informal, or neutral? Would we ever use kita instead in a similar sentence?

Kami is neutral in terms of formality; it’s used in both casual and formal situations when the listener is not included in “we.”
You’d use kita (also neutral in formality) if you want to include the listener:

Malam ini kita berjalan di lapangan yang terasa luas.
= Tonight we (you and I / all of us including you) are walking in the field that feels spacious.

So the choice between kami and kita is about who is included, not about being polite or casual.