Он потерял веру в успех.

Потерял is the past tense masculine singular form of потерять.

It matches он, which means he.

• он потерял = he lost
• она потеряла = she lost
• они потеряли = they lost

In Russian, past tense verbs change for gender in the singular and number in the plural.

The dictionary form is потерять.

This is a perfective verb, so it presents the action as completed: he lost faith.

Its imperfective partner is терять:

• Он терял веру в успех. = He was losing faith in success / used to lose faith in success.
• Он потерял веру в успех. = He lost faith in success.

So in your sentence, the focus is on the result: the faith is gone.

Because вера is the direct object of потерял, and direct objects often go into the accusative case.

• nominative: вера
• accusative: веру

So:

• вера = faith/belief as the subject form
• потерял веру = lost faith

This is very common in Russian:

• иметь надежду → actually надежду in the accusative
• любить музыку
• читать книгу

Because after вера в meaning belief/faith in, Russian uses the accusative case.

So:

• вера в успех
• верить в успех

Here успех is a masculine inanimate noun, and for many such nouns, the accusative looks the same as the nominative:

• nominative: успех
• accusative: успех

That is why the form does not change visibly.

В успехе would be the prepositional case and would usually mean something like in success, which is not what this sentence is saying.

Yes, it is a very natural and common Russian expression.

Some common patterns are:

• вера в успех = belief in success
• вера в себя = belief in oneself
• вера в будущее = belief in the future

So потерять веру в успех is a normal, idiomatic way to say that someone stopped believing success was possible.

In this sentence, вера is closer to belief or faith than to simple factual opinion.

It suggests a fairly deep sense that success is possible.

Depending on context, English might translate it as:

• faith in success
• belief in success
• sometimes even confidence in success

But вера often sounds a bit stronger and more emotional than plain belief.

They are similar, but not exactly the same.

• потерять веру в успех = to lose faith/belief in success
• потерять надежду на успех = to lose hope of success

A simple way to feel the difference:

• вера = inner conviction, belief
• надежда = hope, expectation that something may still happen

So потерять веру в успех can sound a bit more psychological or philosophical, while потерять надежду на успех often focuses more on giving up hope.

Yes, often it can be omitted if the subject is already clear from context.

Russian frequently drops subject pronouns when they are not needed.

So both can work:

• Он потерял веру в успех.
• Потерял веру в успех. = natural in context, especially in speech or narrative

Using он can make the subject clearer or slightly more explicit.

Yes. Russian word order is flexible, although the neutral order here is:

Он потерял веру в успех.

Other orders are possible for emphasis, for example:

• Веру в успех он потерял.
  Emphasizes faith in success
• Он веру в успех потерял.
  Also possible, often with a spoken or stylistic emphasis

The basic meaning stays the same, but the focus changes.

Because Russian has no articles like a, an, or the.

So успех can mean:

• success
• the success
• a success

The exact meaning depends on context.

In this sentence, English usually uses the general idea success, not a specific countable success.

The stress is:

• он потеря́л ве́ру в успе́х

More specifically:

• потеря́л
• ве́ру
• успе́х

Stress is important in Russian, because it is not always predictable and can affect pronunciation quite a lot.