Πιστεύουμε στη δικαιοσύνη.

Πιστεύουμε means we believe.

It comes from the verb πιστεύω = I believe.
The ending -ουμε shows that it is:

• present tense
• first person plural
• so, we believe

In this sentence, it is the main verb.

Greek often leaves out subject pronouns when they are not needed.

So instead of saying Εμείς πιστεύουμε, Greek usually just says Πιστεύουμε, because the verb ending already tells you the subject is we.

You could add εμείς if you want emphasis or contrast, for example:

• Εμείς πιστεύουμε στη δικαιοσύνη. = We believe in justice.

That sounds more emphatic, as if contrasting we with someone else.

στη is a contracted form of:

• σε = in, to, at
• τη(ν) = the, feminine accusative singular

So:

• σε + τη(ν) → στη(ν)

In this sentence, στη is best translated as in, because Greek uses πιστεύω σε... for believe in...

So:

• στη δικαιοσύνη = in justice

Both στη and στην come from σε + την.

The final -ν is kept or dropped depending on the sound that follows. Before some consonants, Greek commonly drops it. Since δικαιοσύνη starts with δ, the normal form here is:

• στη δικαιοσύνη

You will often see στην before a vowel or certain consonants, for example:

• στην Αθήνα

So στη δικαιοσύνη is the expected form here.

It is in the accusative singular, because the preposition σε takes the accusative.

Here is the pattern:

• nominative: η δικαιοσύνη
• accusative: τη(ν) δικαιοσύνη

Notice that the noun δικαιοσύνη itself looks the same in nominative and accusative singular. What changes clearly is the article:

• η → τη(ν)

So the case is shown mainly by the article here.

That is very normal in Greek.

Greek often uses the definite article with abstract nouns, general ideas, and nouns that English may leave without an article.

So:

• η δικαιοσύνη literally looks like the justice
• but in natural English translation, it is usually just justice

This does not mean Greek is talking about one specific kind of justice only. It is simply a common Greek structure.

Not always. πιστεύω can be used in different ways.

Common patterns include:

• πιστεύω σε κάτι / κάποιον = I believe in something / someone
• πιστεύω ότι... or πιστεύω πως... = I believe that...
• πιστεύω κάποιον = I believe someone, meaning I think someone is telling the truth

So in this sentence:

• Πιστεύουμε στη δικαιοσύνη means
• We believe in justice

That is the believe in pattern.

Yes. Greek word order is more flexible than English word order.

The neutral, straightforward order here is:

• Πιστεύουμε στη δικαιοσύνη.

But you could also say:

• Στη δικαιοσύνη πιστεύουμε.

That would put more emphasis on justice, almost like:

• It is in justice that we believe
• or Justice is what we believe in

So the original sentence is the most neutral and natural basic version.

A rough pronunciation is:

• pee-STEV-oo-meh stee thee-keh-yoh-SEE-nee

A few useful pronunciation notes:

• Πιστεύουμε has the stress on -τεύ-
• δικαιοσύνη has the stress on -σύ-
• δ sounds like th in this, not like English d
• η, ι, and υ are all pronounced like ee

So a more careful breakdown is:

• Πι-στε-ύ-με
• στη δι-και-ο-σύ-νη

Yes. δικαιοσύνη is feminine.

You can see that from its dictionary form:

• η δικαιοσύνη

That is why the article in the sentence is the feminine form:

• τη(ν) inside στη

So the grammar matches:

• feminine noun
• feminine accusative article
• after σε

No. Even though σε can mean in, to, or at depending on context, you should translate the whole expression naturally.

With πιστεύω σε, the normal English meaning is:

• believe in

So the natural translation is:

• We believe in justice.

This is a good example of why it is better to learn the whole pattern, not just each word separately.