Ожидаемый автобус так и не приехал.

It means the bus that was expected / awaited / the bus people were waiting for.

In this sentence, ожидаемый does not mean that the bus itself is doing the expecting. It means the bus was the object of expectation. So the idea is:

• people expected the bus
• people were waiting for the bus
• but it never arrived

Depending on context, English might render it as the expected bus, the awaited bus, or more naturally the bus we were waiting for.

It is originally a participle, more specifically a present passive participle from ожидать.

So:

• ожидать = to expect, await
• ожидаемый = expected, awaited, being expected

In many real sentences, though, it behaves very much like an adjective. That means it declines like an adjective and agrees with the noun in gender, number, and case.

A useful detail: it comes from ожидать, not directly from ждать. English speakers often learn ждать first, but forms like ожидаемый are based on ожидать and sound more natural in this kind of written style.

Because автобус is the subject of the sentence: the bus is the thing that did not arrive.

So both words are in the:

• masculine
• singular
• nominative

That is why you get:

• ожидаемый автобус

The adjective/participle must agree with the noun:

• ожидаемый автобус = masculine singular nominative
• ожидаемая машина = feminine singular nominative
• ожидаемые автобусы = plural nominative

Russian has no articles, so it does not mark the and a directly.

Here, the noun feels definite because of context and because ожидаемый makes it specific: this is not just any bus, but a particular bus that was expected.

So in English, the bus is usually the most natural translation.

Так и не is a very common Russian pattern that adds a strong sense of an expected result failing to happen.

So:

• Автобус не приехал = The bus didn’t arrive.
• Автобус так и не приехал = The bus never did arrive / The bus still didn’t arrive / The bus failed to arrive after all.

It often implies:

• people expected it to happen
• maybe they waited for it
• but the expected event never occurred

So так и не adds disappointment, frustration, or emphasis.

Because приехал is perfective, and that fits this situation.

The sentence is about one expected completed event: the bus was supposed to arrive, but that arrival never happened. Russian normally uses the perfective in this pattern:

• так и не + perfective verb

So:

• так и не приехал = never arrived

If you used не приезжал, it would sound more like:

• did not come at some point
• was not in the habit of coming
• did not make visits

That is not the idea here. Here we want a single expected arrival that failed to happen.

With transport, Russian can use both, depending on style and nuance.

• приехал literally focuses on arriving by vehicle
• пришёл is also very common in everyday speech for buses, trains, trams, etc., meaning simply came / arrived

So both of these are possible:

• Автобус так и не приехал
• Автобус так и не пришёл

The version with приехал is perfectly correct and slightly more literal in terms of movement by transport.

Yes, it is natural and understandable, but it sounds a bit more written or bookish because of ожидаемый.

In everyday speech, a Russian speaker might more often say:

• Автобус, который ждали, так и не приехал.
• Автобус так и не приехал.

So the given sentence is fine, but it is a little more formal than casual conversation.

Yes. Russian word order is flexible, and changing it changes emphasis more than basic meaning.

For example:

• Ожидаемый автобус так и не приехал.
  Fairly neutral, slightly written.

• Так и не приехал ожидаемый автобус.
  More dramatic or literary; it foregrounds the failure to arrive.

• Автобус так и не приехал.
  Very natural if the listener already knows which bus you mean.

So the original word order is correct, but not the only possible one.

No. The sentence leaves that unspecified.

Ожидаемый tells us that the bus was expected by someone, but it does not say exactly who. That information has to come from context.

If needed, Russian can state it explicitly, for example:

• ожидаемый пассажирами автобус = the bus expected by the passengers

But in your sentence, the focus is on the bus and the fact that it never arrived, not on who was waiting.

A Russian speaker can use ожидаемый, especially in written narration, journalism, or a slightly elevated style. But in ordinary conversation, many speakers would prefer a clause instead of the participle.

More conversational options are:

• Автобус, который ждали, так и не приехал.
• Мы так и не дождались автобуса.

So ожидаемый автобус is correct, but not the most everyday way to express the idea.