У меня в кошельке только мелочь.

In everyday Russian, possession is usually expressed with the pattern у + genitive rather than with a direct equivalent of English to have.

• у means something like by / at
• меня is the genitive form of я

So У меня literally means at me or by me, and Russian uses that to express I have.

This is much more natural than using иметь in normal conversation.
So:

• У меня есть книга = I have a book
• У меня в кошельке только мелочь = I have only change in my wallet

Russian often leaves out есть in the present tense when it means is/are or when it appears in possession structures.

So instead of saying:

• У меня есть в кошельке только мелочь

Russian normally just says:

• У меня в кошельке только мелочь

The idea of there is / I have is understood from the structure.

A rough literal breakdown is:

• У меня = with me / I have
• в кошельке = in the wallet
• только мелочь = only change

Меня is the genitive form of я.

That is because the preposition у requires the genitive case when it means by / at / in the possession of.

So:

• я = I
• меня = of me / me in the genitive

This is a very common pattern:

• у меня = I have
• у тебя = you have
• у него = he has
• у неё = she has

Because в кошельке describes location, not movement.

With в, Russian usually works like this:

• в + accusative = motion into something
• в + prepositional = location inside something

Here, the meaning is in the wallet, so Russian uses the prepositional case:

• в кошельке = in the wallet

Compare:

• Я положил деньги в кошелёк. = I put the money into the wallet.
• Деньги в кошельке. = The money is in the wallet.

The dictionary form is кошелёк.

In the sentence, it changes to кошельке because it is in the prepositional singular after в.

So:

• dictionary form: кошелёк
• in the sentence: в кошельке

This can be tricky because the stress changes too:

• кошелёк
• в кошельке

Also, Russian often writes е instead of ё in ordinary texts, so learners need to be ready for that.

Мелочь is nominative singular.

In this kind of possession sentence, the thing that exists or is possessed is normally in the nominative in an affirmative statement:

• У меня книга.
• У меня есть книга.
• У меня в кошельке только мелочь.

If the sentence were negative with нет, Russian would usually switch to the genitive:

• У меня нет мелочи. = I have no change.

No. Мелочь is a common Russian noun meaning small change / loose change, and it is usually treated as a singular mass noun, much like English change.

So even if it refers to several coins, Russian still says:

• мелочь

This word does not just mean individual coins one by one. It means small money as a category.

Compare:

• мелочь = small change / loose change
• монеты = coins
• мелкие деньги = small-denomination money

So this sentence is talking about change, not specifically counting separate coins.

Только means only or just.

Here it limits мелочь, so the idea is that the wallet contains only change, and nothing else of value or no larger bills.

The most natural interpretation is:

• in my wallet, there is only change

Russian word order is flexible, but in this sentence только naturally goes right before the thing it restricts:

• только мелочь = only change

Yes. Russian word order is flexible, and changing it usually changes emphasis, not the basic meaning.

The given sentence is a neutral, natural version:

• У меня в кошельке только мелочь.

Other possible orders could be:

• В кошельке у меня только мелочь.
  This puts more focus on in the wallet.

• Только мелочь у меня в кошельке.
  This strongly emphasizes only change.

• У меня только мелочь в кошельке.
  Possible, but a little less neutral in tone.

So the original order is a very good default sentence for everyday speech.

It can, but it is not necessary here.

Russian often leaves out possessive adjectives like my when possession is already clear from context. Since the sentence starts with У меня, it is already obvious that the wallet is mine unless the context suggests otherwise.

So:

• У меня в кошельке только мелочь. = natural
• У меня в моём кошельке только мелочь. = possible, but more explicit than needed

Russian usually prefers the simpler version unless there is a reason to stress my wallet specifically.