Сколько ни жди, автобус всё равно не приезжает вовремя.

It means something like no matter how long you wait or however long you wait.

This pattern expresses concession: even if the action continues for a long time, the result still does not change.

So:

• Сколько ни жди = however much / however long you wait
• whole sentence = No matter how long you wait, the bus still doesn’t arrive on time.

A very close paraphrase is:

• Сколько бы ты ни ждал, автобус всё равно не приезжает вовремя.

The original is shorter and more natural in this kind of saying.

Yes, жди is formally the imperative singular of ждать.

But in expressions like сколько ни жди, Russian often uses the imperative in a special, idiomatic way to mean something general like:

• however much one waits
• no matter how much you wait

So here it is not really a command. It is part of a fixed concessive pattern:

• как ни старайся = no matter how hard you try
• что ни говори = whatever you say / no matter what you say
• сколько ни жди = no matter how long you wait

You can think of it as a compact conversational alternative to a fuller clause like сколько бы ни ждал.

In this sentence, ни is part of the pattern that gives the meaning no matter how... / however....

So:

• сколько ни жди = however long you wait
• как ни странно = strangely enough / however strange it may seem
• что ни делай = whatever you do

This ни is different from ordinary negation не.

• не usually simply negates:
  автобус не приезжает = the bus does not arrive
• ни in this kind of structure strengthens the concessive/indefinite meaning:
  сколько ни жди = no matter how long you wait

So in your sentence, both appear:

• ни in the first part: concessive meaning
• не in the second part: actual negation of приезжает

Russian often leaves out words that are obvious from context.

Here, after жди, the implied object is the bus, so the full idea is:

• Сколько ни жди автобус / автобуса...

But because the second clause immediately mentions автобус, Russian naturally omits it in the first clause.

This kind of omission is very common when the meaning is clear.

If you wanted to make it explicit, you could say:

• Сколько ни жди автобуса, он всё равно не приезжает вовремя.

That sounds completely normal too.

Normally it would be автобуса:

• ждать автобуса = to wait for the bus

That is because ждать commonly takes the genitive object in standard Russian.

So the expanded version would usually be:

• Сколько ни жди автобуса, он всё равно не приезжает вовремя.

You may sometimes encounter ждать автобус in modern speech, especially colloquially, but for a learner, ждать + genitive is the safest and most standard choice here.

Here всё равно means all the same, anyway, or still.

It emphasizes that the second clause remains true despite the first clause:

• Сколько ни жди = no matter how long you wait
• автобус всё равно не приезжает вовремя = the bus still doesn’t arrive on time anyway

So всё равно adds the sense of:

• despite that
• even so
• it makes no difference

Without it, the sentence would still be grammatical:

• Сколько ни жди, автобус не приезжает вовремя.

But всё равно makes the contrast stronger and more idiomatic.

Because не приезжает describes a habitual, repeated, or general situation.

• приезжает = imperfective present
• here it means something like doesn’t arrive on time (as a regular pattern)

So the sentence is not mainly about one single future bus. It means:

• this keeps happening
• the bus is habitually late
• waiting longer does not help

If you used не приедет, that would sound more like a single future event:

• Сколько ни жди, автобус всё равно не приедет вовремя.
  = No matter how long you wait, the bus still won’t arrive on time.

That version is also possible, but it shifts the meaning toward one specific expected arrival in the future.

It can feel a bit general, like a complaint about a typical situation, even though автобус is singular.

Russian often uses the singular in this kind of statement to represent:

• a typical instance
• the bus you are waiting for
• the bus service as experienced by the speaker

So depending on context, it may mean either:

• this particular bus never comes on time, or
• the bus is always late as a general complaint

If you wanted to make it clearly plural/general, you could say:

• Автобусы всё равно не приезжают вовремя.

But the singular is very natural in the original sentence.

Because Russian often uses the singular to talk about a typical or relevant item in context.

English does this too sometimes:

• The bus never comes on time.

That does not always mean one unique bus forever; it can mean the bus I’m talking about / the bus service in this situation.

So:

• автобус here is not strange
• it refers to the bus the speaker is waiting for, or to the bus as a typical recurring problem

Using the plural would change the nuance slightly, making it sound more broadly about buses as a category.

Вовремя means on time, at the proper time, or when it is supposed to.

So:

• приезжает вовремя = arrives on time
• не приезжает вовремя = does not arrive on time

It is a very common adverb.

Compare:

• Я пришёл вовремя. = I arrived on time.
• Он никогда не приходит вовремя. = He never comes on time.

In your sentence, it means the bus fails to arrive at the scheduled or expected time.

Yes, to some extent, but the original order is very natural.

Original:

• Сколько ни жди, автобус всё равно не приезжает вовремя.

This order works well because:

1. the concessive clause comes first: no matter how long you wait
2. then the main point comes after it

You could also say:

• Автобус всё равно не приезжает вовремя, сколько ни жди.

That is also understandable, but it feels a bit more like an afterthought or spoken emphasis.

You could omit or move всё равно in some cases, but the original placement is the most idiomatic because it clearly links the two ideas:

• waiting longer changes nothing
• the bus is still late

Yes. A fuller version could be:

• Сколько бы ты ни ждал, автобус всё равно не приезжает вовремя.

This version makes several things more explicit:

• бы marks the concessive/conditional flavor
• ты makes the subject visible
• ждал is a past-form element used in this kind of conditional-style structure

But in everyday Russian, the shorter version

• Сколько ни жди...

is very common, compact, and expressive.

For a learner, it is useful to recognize both patterns:

• Сколько ни жди...
• Сколько бы ты ни ждал...

They mean almost the same thing here.