На перехресті тротуар широкий, і там зручно чекати на зелене світло.

Because на can mean on / at when talking about location, and after it Ukrainian uses the locative case.

• dictionary form: перехрестя = intersection
• locative singular: на перехресті = at the intersection

So на перехресті answers the question де? = where?

Compare:

• на перехресті = at the intersection
• на перехрестя = onto/to the intersection (motion toward it, usually accusative)

In Ukrainian, the verb to be is normally left out in the present tense.

So:

• тротуар широкий literally looks like sidewalk wide
• but it means the sidewalk is wide

This is completely normal Ukrainian grammar.

Compare:

• Він студент. = He is a student.
• Кімната велика. = The room is big.

In past or future, forms of бути appear more clearly:

• Тротуар був широкий. = The sidewalk was wide.
• Тротуар буде широкий / широким. = The sidewalk will be wide.

Because it agrees with тротуар in gender, number, and case.

• тротуар is masculine singular
• so the adjective must also be masculine singular nominative
• that gives широкий

Agreement patterns:

• широкий тротуар = wide sidewalk (masculine)
• широка вулиця = wide street (feminine)
• широке перехрестя = wide intersection (neuter)
• широкі дороги = wide roads (plural)

Там means there. It refers back to the place already mentioned: на перехресті.

So the sentence structure is roughly:

• At the intersection, the sidewalk is wide, and there it is convenient to wait for the green light.

It makes the second part sound more natural and connected to the location. Without там, the sentence would still be grammatical:

• На перехресті тротуар широкий, і зручно чекати на зелене світло.

But там helps emphasize in that place.

Here зручно is used as a predicative adverb in an impersonal construction.

It means something like:

• it is convenient
• it is comfortable
• it is easy / practical

So:

• там зручно чекати = it is convenient to wait there

There is no real subject like it in Ukrainian; English adds it because English needs a subject.

Similar examples:

• Тут тепло. = It is warm here.
• Мені зручно сидіти тут. = It is comfortable for me to sit here.
• Було важко працювати. = It was hard to work.

Good question. Чекати can be used in more than one way.

A common pattern is:

• чекати на + accusative

So:

• чекати на автобус = wait for the bus
• чекати на друга = wait for a friend
• чекати на зелене світло = wait for the green light

You may also see чекати without на, often with the genitive, especially in more formal or literary usage:

• чекати автобуса
• чекати друга

For many learners, чекати на + accusative is a very useful and natural pattern to remember.

Because світло is a neuter singular noun, and the adjective has to agree with it.

• світло = light, signal
• neuter singular adjective form of зелений = зелене

So:

• зелене світло = green light

This phrase often refers specifically to the traffic signal.

Agreement examples:

• зелений сигнал = green signal (masculine)
• зелена лампа = green lamp (feminine)
• зелене світло = green light (neuter)

Because here на belongs to the pattern чекати на + accusative, and зелене світло is in the accusative case.

But for neuter inanimate singular nouns, the accusative often looks exactly the same as the nominative.

So:

• nominative: зелене світло
• accusative: зелене світло

No visible change happens, even though the case has changed grammatically.

You can see the difference more clearly with other nouns:

• чекати на брата (accusative of брат)
• чекати на машину (accusative of машина)

Because і is joining two clauses:

1. тротуар широкий
2. там зручно чекати на зелене світло

Each clause has its own predicative center, so a comma is normally used before і.

Very roughly:

• The sidewalk is wide, and it is convenient to wait there for the green light.

If і joined only two simple words, there would usually be no comma:

• широкий і чистий тротуар = a wide and clean sidewalk

Not here. Even though на often means on / onto, in this sentence it is part of the verb pattern чекати на = to wait for.

So you should understand:

• чекати на зелене світло = wait for the green light

not:

• wait onto the green light

This is a good example of why prepositions often need to be learned together with the verb.

Yes. Ukrainian word order is fairly flexible, and changing the order changes the emphasis more than the basic meaning.

Original:

• На перехресті тротуар широкий, і там зручно чекати на зелене світло.

Possible variations:

• Тротуар на перехресті широкий, і там зручно чекати на зелене світло.
• На перехресті широкий тротуар, і там зручно чекати на зелене світло.

The original version puts the location first, which sounds natural if the speaker is describing that place.

In this context, зелене світло most naturally means the green traffic signal.

Ukrainian often uses світло in this expression the same way English says green light. Depending on context, it can refer to:

• the green traffic light itself
• the green signal/permission to go

In this sentence, because of перехресті and чекати, the traffic meaning is very clear.

Yes, you may encounter чекати зеленого світла too. That uses чекати + genitive instead of чекати на + accusative.

So both patterns can exist:

• чекати на зелене світло
• чекати зеленого світла

For a learner, чекати на + accusative is often easier to use consistently in everyday speech. The version in your sentence sounds very natural.