Η πέτρα είναι βαριά.

Η is the feminine singular form of the definite article, so here it means the.

In this sentence:

• Η πέτρα = the stone

Greek articles change for gender, number, and case. Here πέτρα is a feminine singular noun, so it takes η.

In Greek, grammatical gender is not the same thing as real-world sex.

πέτρα is a grammatically feminine noun, so words that go with it, such as the article and adjective, must also be feminine. This does not mean the stone is female in any literal sense.

So:

• η matches the feminine noun πέτρα
• βαριά also matches it because adjectives agree with the noun

Greek adjectives must agree with the noun they describe in:

• gender
• number
• case

Since πέτρα is feminine singular nominative, the adjective must also be feminine singular nominative.

So the forms are:

• masculine: βαρύς
• feminine: βαριά
• neuter: βαρύ

That is why the sentence uses βαριά.

είναι is the present tense form of the verb to be.

In this sentence it means is.

A useful thing for learners to know is that είναι is used for:

• he is
• she is
• it is

So Greek does not need a separate word here for it.

Greek often leaves subject pronouns out when they are clear from the verb or from context.

English usually says It is heavy, but Greek can simply say:

• Η πέτρα είναι βαριά

The noun η πέτρα already tells you what the subject is, so no extra pronoun is needed.

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

Η πέτρα είναι βαριά is the most neutral, straightforward order:

• subject: Η πέτρα
• verb: είναι
• adjective/complement: βαριά

But Greek can change the order for emphasis. For example, Βαριά είναι η πέτρα can sound more emphatic, something like The stone is heavy with stress on heavy.

So the given order is the normal, neutral one.

The accent marks show which syllable is stressed when you pronounce the word.

• πέτρα → stress on the first syllable
• είναι → stress on the first syllable
• βαριά → stress on the last syllable

For an English speaker, paying attention to stress is important, because it is a regular and meaningful part of Greek spelling and pronunciation.

No. In Modern Greek, Η is not pronounced like English h.

It is pronounced like ee in see.

So:

• Η sounds like ee
• η πέτρα sounds roughly like ee PET-ra

This is a common surprise for English speakers, because the Greek letter looks like English H, but it does not sound like h.

A rough pronunciation guide is:

ee PET-ra EE-ne va-ree-A

More carefully:

• Η = ee
• πέτρα = PET-ra
• είναι = EE-ne
• βαριά = va-ree-A

This is only an approximation in English spelling, but it can help as a first step.

This particular form, βαριά, is the feminine singular form.

If the noun changed, the adjective would usually change too. For example:

• masculine: βαρύς
• feminine: βαριά
• neuter: βαρύ

So βαριά is used because it agrees with πέτρα, which is feminine singular.

By itself, it can simply mean that the stone is heavy. Greek είναι covers the kind of meaning English usually expresses with is.

In practice, context tells you whether the description is just an observation right now or a more general characteristic. In a simple sentence like this, it is just a normal statement describing the stone.

In a normal sentence like this, η is expected if you mean the stone.

Without the article, the sentence would sound unusual in standard Greek unless there were a special context, such as headings, poetic style, or certain kinds of emphasis.

So for ordinary usage:

• Η πέτρα είναι βαριά = the natural way to say it

Greek uses the definite article very regularly with nouns when talking about a specific thing.

Since this sentence is about a particular stone, Greek naturally says:

• Η πέτρα = the stone

English learners sometimes want to focus only on the noun, but in Greek the article is an important part of the noun phrase and should be learned together with the noun whenever possible.