El peatón camina con cuidado por la acera cuando el semáforo cambia de color.

In Spanish, singular countable nouns normally need an article, much more often than in English.

So:

• el peatón = the pedestrian
• el semáforo = the traffic light

Spanish usually does not say just peatón camina... in a normal sentence. The article helps make the sentence sound complete and natural.

Also, both nouns are masculine singular, so they take el.

Spanish nouns have grammatical gender, so every noun is usually treated as masculine or feminine.

Here:

• peatón is masculine
• semáforo is masculine
• acera is feminine

There is not always a logical reason, so gender often has to be learned with the noun:

• el peatón
• el semáforo
• la acera

Some endings can help:

• nouns ending in -o are often masculine, like semáforo
• nouns ending in -a are often feminine, like acera

But peatón is a good reminder that endings do not always make gender obvious.

No. Peatón means pedestrian, specifically a person who is walking, especially in the context of streets and traffic.

So:

• persona = person
• peatón = pedestrian

Because the sentence talks about a sidewalk and a traffic light, peatón is the precise word.

Spanish often uses the simple present where English might use either walks or is walking.

So camina can mean:

• walks
• is walking

The exact English translation depends on context.

Spanish does have está caminando, but that form focuses more strongly on the action being in progress right now. In many ordinary descriptions, the simple present sounds more natural.

Con cuidado is a very common Spanish expression meaning carefully or with care.

Literally:

• con = with
• cuidado = care

So camina con cuidado = walks carefully

Spanish can also use adverbs like cuidadosamente, but con cuidado is very common, natural, and often sounds less formal.

Compare:

• Camina con cuidado. = Walk carefully.
• Camina cuidadosamente. = Also correct, but often a bit more formal or bookish.

Por often expresses movement along, through, or by way of a place.

So:

• camina por la acera = walks along the sidewalk

If you said en la acera, it would emphasize location more than movement:

• Está en la acera = He is on the sidewalk

Both can be possible in some contexts, but here por la acera is the most natural way to describe someone moving along it.

Yes. In Spain, acera is the standard word for sidewalk.

In other Spanish-speaking countries, other words may be used, for example:

• banqueta
• vereda
• andén in some contexts

But for Spanish from Spain, acera is exactly the right word.

This is a very common question because cuando can be followed by either the indicative or the subjunctive.

Here, cambia is in the present indicative because the sentence expresses a general, habitual, or factual situation:

• El peatón camina con cuidado por la acera cuando el semáforo cambia de color.

This sounds like a general truth or a repeated action.

You would use the subjunctive, cambie, if you were talking about a future event that has not happened yet:

• El peatón caminará con cuidado cuando el semáforo cambie de color.
• The pedestrian will walk carefully when the traffic light changes color.

So:

• cuando + indicative = habitual, repeated, known, factual
• cuando + subjunctive = future or not-yet-realized event

In Spanish, cambiar de + noun is a very common structure for to change in/to change to a different...

So:

• cambiar de color = to change color

The de is part of the normal expression.

Other examples:

• cambiar de idea = to change one’s mind
• cambiar de ropa = to change clothes
• cambiar de dirección = to change direction

So el semáforo cambia de color is idiomatic Spanish.

Yes, it is understandable and grammatically correct.

That said, in real-life traffic situations, Spanish speakers might often be more specific and say:

• cuando el semáforo se pone en verde
• cuando el semáforo se pone rojo
• cuando cambia a verde
• cuando cambia a rojo

Those versions mention the exact color. But cambia de color is still fine if the point is simply that the light changes.

Because its subject is el semáforo, which is singular.

Breakdown:

• el peatón camina... → subject: el peatón → verb: camina
• cuando el semáforo cambia... → subject: el semáforo → verb: cambia

Each verb agrees with its own subject.

Yes. The Spanish present tense is flexible.

Depending on context, camina and cambia can express:

• a habitual action
• a general truth
• something happening now

So this sentence could be understood as:

• a general statement about what a pedestrian does
• or a description of what is happening in a scene

Context tells you which meaning is intended.

The accent marks show which syllable is stressed.

• peatón → stress on the last syllable: pea-TÓN
• semáforo → stress on the second syllable: se-MÁ-fo-ro

They are not optional; they are part of the correct spelling.

Without the accents, the words would either be pronounced differently under normal spelling rules or simply be incorrect.

A few pronunciation points are especially useful for Spain Spanish:

• acera: in most of Spain, the c before e sounds like English th in think
  So it sounds roughly like a-THEH-ra

• cambia: here the c is before a, so it sounds like k
  Roughly: KAM-bya

• cuidado: the cu sounds like kw
  Roughly: kwee-DA-do

• peatón: often pronounced roughly pe-a-TON, with a clear stress at the end

• semáforo: roughly se-MA-fo-ro

In Latin American Spanish, acera would usually have an s sound instead of the Spain th sound.

Yes, but the original order is the most neutral and straightforward.

Original:

• El peatón camina con cuidado por la acera cuando el semáforo cambia de color.

You could rearrange parts for emphasis, for example:

• Cuando el semáforo cambia de color, el peatón camina con cuidado por la acera.

That version is also correct. It just puts the time clause first.

Spanish word order is flexible, but not random. The original sentence is a good standard model.