Η δικαιοσύνη είναι σημαντική.

Η is the feminine singular definite article, basically the.

So η δικαιοσύνη is literally the justice. In Greek, abstract nouns often appear with the definite article more naturally than they do in English, so the best English translation is usually just justice, not necessarily the justice.

Also, η shows that δικαιοσύνη is:

• feminine
• singular
• here, in the nominative case

In Greek, every noun has a grammatical gender: masculine, feminine, or neuter. This is a grammar category, not always something logical from meaning.

Δικαιοσύνη happens to be a feminine noun, which is why it takes:

• the feminine article η
• the feminine adjective form σημαντική

A learner usually just has to memorize a noun together with its article, for example:

• η δικαιοσύνη
• η αγάπη
• η ελευθερία

Because Greek adjectives must agree with the noun they describe.

Since δικαιοσύνη is:

• feminine
• singular

the adjective must also be feminine singular, so we get σημαντική.

Compare:

• η δικαιοσύνη είναι σημαντική = justice is important
• ο νόμος είναι σημαντικός = the law is important
• το θέμα είναι σημαντικό = the issue is important

So the ending changes to match the gender of the noun.

Είναι is the present tense form of the verb είμαι, meaning to be.

In this sentence it means is:

• Η δικαιοσύνη είναι σημαντική. = Justice is important.

Useful forms of είμαι are:

• είμαι = I am
• είσαι = you are
• είναι = he/she/it is; they are

So είναι can mean either is or are, depending on context.

Greek often does not need an explicit subject pronoun the way English does, because the verb form already gives grammatical information.

In this sentence, though, the subject is not a pronoun like it anyway. The subject is the noun phrase η δικαιοσύνη.

So the structure is simply:

• η δικαιοσύνη = justice
• είναι = is
• σημαντική = important

Greek does not need a dummy subject like English sometimes does.

It is an adjective meaning important.

In this sentence, it functions as a predicate adjective, meaning it comes after the verb είναι and describes the subject.

So:

• η δικαιοσύνη = the subject
• είναι = linking verb
• σημαντική = adjective describing the subject

This is similar to English:

• Justice is important

It is in the nominative case, because it is the subject of the sentence.

The adjective σημαντική is also nominative feminine singular, agreeing with δικαιοσύνη.

So the sentence uses:

• η δικαιοσύνη = nominative subject
• σημαντική = nominative predicate adjective

This is very common with είμαι.

A rough pronunciation guide is:

ee thee-keh-oh-SOO-nee EE-neh see-man-dee-KEE

A few helpful notes:

• η sounds like ee
• δικαιοσύνη is stressed on σύ
• είναι is pronounced roughly EE-neh
• σημαντική is stressed on the last syllable: κή

The accent marks show you where the stress goes:

• δικαιοσύνη
• είναι
• σημαντική

Greek uses accent marks to show the stressed syllable.

In είναι, the stress falls on the first syllable: ΕΙ-ναι.

Accent marks are an important part of correct spelling in Modern Greek, so learners should pay attention to them. They are not optional in normal writing.

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

The neutral, straightforward order is:

• Η δικαιοσύνη είναι σημαντική.

But Greek can change the order for emphasis, for example:

• Σημαντική είναι η δικαιοσύνη.

That would sound more marked or emphatic, something like Justice is what is important or Important is justice, depending on context.

For a beginner, the original order is the safest and most natural pattern to learn.

That is a very common difference between Greek and English.

Greek often uses the definite article with:

• abstract nouns
• general ideas
• whole categories
• subjects in a general sense

So η δικαιοσύνη is perfectly natural Greek even when English simply says justice.

This does not always mean Greek is being more specific. Often it is just the normal Greek way of expressing the noun.

No. They look very similar, but they are different words.

• η without an accent = the for feminine singular nouns
• ή with an accent = or

So in your sentence:

• Η δικαιοσύνη = Justice / The justice

But:

• ή would mean or, which would not make sense here.

This is a very common beginner confusion, so it is good to notice the accent carefully.

In some contexts Greek can omit the article, but here that would sound less natural as a neutral statement.

The most natural standard sentence is:

• Η δικαιοσύνη είναι σημαντική.

As a learner, it is best to keep the article here. Greek uses articles more often than English does, and leaving them out can make your Greek sound unnatural even if the meaning is still understandable.