Joku varasti pyöräni.

Joku means someone or somebody.

It is an indefinite pronoun: you know that a person exists, but you do not know who it is, or you do not want to say who it is.

So in this sentence, Joku varasti pyöräni, joku is the subject: the unknown person who did the stealing.

A useful comparison:

• joku = someone / somebody
• kukaan = anyone / no one, usually in negative sentences or questions

For example:

• Joku tuli. = Someone came.
• Ei kukaan tullut. = No one came.

Varasti is the past tense, third person singular form of the verb varastaa, which means to steal.

So:

• varastaa = to steal
• varasti = stole

In this sentence, the subject is joku (someone), which is grammatically third person singular, so the verb is also third person singular.

Very roughly:

• Minä varastin = I stole
• Sinä varastit = you stole
• Hän/Joku varasti = he/she/someone stole

So varasti is the natural form here because the action happened in the past and the subject is singular.

The ending -ni is a possessive suffix meaning my.

So:

• pyörä = bike / bicycle
• pyöräni = my bike

Finnish often shows possession by adding a suffix directly to the noun.

Some common possessive suffixes are:

• -ni = my
• -si = your
• -nsa / -nsä = his / her / their

Examples:

• kirja = book

• kirjani = my book

• auto = car
• autosi = your car

So pyöräni is literally bike-my, but in natural English that is my bike.

Yes. Minun pyöräni also means my bike.

In standard Finnish, the full form with the pronoun is possible and often used when you want to be clear or slightly more emphatic:

• pyöräni = my bike
• minun pyöräni = my bike

The difference is mainly about emphasis and style.

For example:

• Joku varasti pyöräni. = Someone stole my bike.
• Joku varasti minun pyöräni. = Someone stole my bike.

In everyday spoken Finnish, people very often avoid the possessive suffix and say something like:

• mun pyörä = my bike

So colloquially, you will often hear:

• Joku varasti mun pyörän.

Finnish does not have articles like English a/an and the.

That means a noun like pyörä can mean:

• a bike
• the bike
• bike

The context tells you which meaning is intended.

In Joku varasti pyöräni, English needs my bike, but Finnish just uses pyöräni without any article. The possessive suffix already shows whose bike it is, so no article is needed.

This is very normal in Finnish:

• Minulla on auto. = I have a car.
• Auto on pihalla. = The car is in the yard.

No separate article appears in either sentence.

This is about the object of the verb.

In Joku varasti pyöräni, pyöräni is the thing that was stolen, so it is the object.

Because the stealing is understood as a completed event, Finnish uses a total object here. With a noun that has a possessive suffix, the form often looks just like the basic noun plus the suffix:

• pyöräni = my bike / my bike as the object here

So even though English learners may expect a visible ending like -n, the possessive suffix changes how the form looks.

A simple learner-friendly way to think about it is:

• varastaa usually takes a whole, completed object when you mean steal something
• with my bike, that appears here as pyöräni

You do not need to change it to pyörän in this sentence.

The most neutral word order here is:

• Joku varasti pyöräni.
• subject + verb + object

That is the most natural basic version.

Finnish word order is more flexible than English, but changing the order usually changes the emphasis.

For example, you might move words around in special contexts, but the neutral sentence is the one you were given.

So for a learner, it is best to treat this as the standard pattern:

• joku = subject
• varasti = verb
• pyöräni = object

This is good standard Finnish.

In everyday speech, many Finns would be more likely to say:

• Joku varasti mun pyörän.

Here:

• mun = spoken form of minun
• pyörän = object form used in speech and standard grammar without a possessive suffix

So the difference is mostly style:

• Joku varasti pyöräni. = standard, neat, written-style or careful spoken Finnish
• Joku varasti mun pyörän. = very natural everyday spoken Finnish

Both mean the same thing.

A rough pronunciation guide for an English speaker is:

• joku ≈ yo-koo
• varasti ≈ va-ra-sti
• pyöräni ≈ something like pyuh-ræ-ni, though the vowels are not exactly like English

A few key points:

• j in Finnish sounds like English y in yes
• r is usually rolled or tapped
• y is like a sound English does not really have; it is similar to saying ee with rounded lips
• ö is also not a normal English sound; it is somewhat like the vowel in some pronunciations of French deux or German schön

Also, Finnish stress is usually on the first syllable of each word:

• JO-ku VA-ras-ti PYÖ-rä-ni

It can mean both.

Pyörä literally means bicycle, but in natural English translation bike is often the most natural choice.

So:

• pyörä = bicycle / bike

If the context is clear, Finnish speakers usually just use pyörä.

So Joku varasti pyöräni could be translated as either:

• Someone stole my bike.
• Someone stole my bicycle.

The meaning is the same.

Because the sentence uses joku (someone) instead of a specific person.

The subject is unknown, so Finnish uses the indefinite pronoun joku rather than hän (he/she).

Also, Finnish does not distinguish between he and she in the third-person singular pronoun:

• hän = he / she

But in this sentence, the speaker does not know who the thief was, so joku is the correct choice.

By itself, the sentence just states a fact: Someone stole my bike.

The emotion is not built into the grammar. However, in real life, the sentence often does imply frustration, annoyance, or shock because of the situation.

If the speaker wants to sound more emotional, Finnish could add extra words or change intonation, for example:

• Joku varasti minun pyöräni! = Someone stole my bike!
• Mun pyörä varastettiin! = My bike got stolen!

So the basic sentence is neutral in grammar, but the situation itself strongly suggests a negative emotion.