Η πορσελάνη είναι ακριβή.

Η is the feminine singular definite article, so literally it means the.

It matches πορσελάνη, which is a feminine noun:

• η πορσελάνη = the porcelain

In this sentence, though, Greek uses the article even where English often does not.

In Greek, the definite article is often used with general statements and with mass nouns more than it is in English.

So:

• Η πορσελάνη είναι ακριβή.
  naturally means
• Porcelain is expensive.

Even though it looks literally like The porcelain is expensive, it can still have a generic meaning. Leaving out the article would usually sound less natural in this kind of sentence.

Because πορσελάνη is simply a noun with grammatical gender: it is feminine.

This does not mean porcelain is female in any real-world sense. Like in many languages, Greek nouns belong to gender classes, and other words must agree with them.

That is why you get:

• η πορσελάνη
• ακριβή and not ακριβός or ακριβό

Greek adjectives must agree with the noun they describe in gender, number, and case.

The noun πορσελάνη is:

• feminine
• singular
• nominative

So the adjective must also be feminine singular nominative:

• masculine: ακριβός
• feminine: ακριβή
• neuter: ακριβό

So:

• Η πορσελάνη είναι ακριβή. = correct

The basic dictionary form is usually ακριβός, or it may be listed as:

• ακριβός, ακριβή, ακριβό

Greek dictionaries often give adjectives in the masculine singular first, even if the sentence uses a feminine or neuter form.

Because here ακριβή is a predicate adjective: it comes after the verb είναι (to be) and describes the subject.

Structure:

• Η πορσελάνη = subject
• είναι = is
• ακριβή = expensive

Compare:

• Η πορσελάνη είναι ακριβή. = The porcelain is expensive.
• Η ακριβή πορσελάνη = the expensive porcelain

So after είναι, the adjective normally stands as part of the predicate.

είναι is the present-tense form of είμαι (to be).

Here it means is.

A useful thing to know is that in Modern Greek, είναι can mean both:

• he/she/it is
• they are

So the form is the same for 3rd person singular and 3rd person plural.
In this sentence, the subject is singular, so it means is.

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

The article also shows nominative feminine singular:

• η πορσελάνη

And the adjective ακριβή is also nominative because it agrees with the subject in this kind of be + adjective sentence.

A good approximation is:

ee por-se-LA-nee EE-ne a-kree-VEE

More carefully:

• Η = ee
• πορσελάνη = por-se-LA-nee
• είναι = EE-ne
• ακριβή = a-kree-VEE

Notes:

• η, ι, υ, ει, οι often sound like ee in Modern Greek.
• The stress falls where the accent mark shows it:
  • πορσελάνη
  • είναι
  • ακριβή

Yes. Greek accent marks show which syllable is stressed, and they are important for correct pronunciation and standard spelling.

In this sentence:

• πορσελάνη → stress on λά
• είναι → stress on the first syllable
• ακριβή → stress on the last syllable

They can also help distinguish words. For example:

• η = the / she
• ή = or

So accents are worth paying attention to from the beginning.

Not always. ακριβός / ακριβή / ακριβό can also mean dear, valuable, or precious, depending on context.

But in a sentence like:

• Η πορσελάνη είναι ακριβή.

the most natural meaning is Porcelain is expensive.

Yes. It can mean either:

• Porcelain is expensive (generic statement), or
• The porcelain is expensive (specific porcelain in context)

The exact meaning depends on the situation. Greek often allows the same wording to be understood either generically or specifically, especially with the article.

The neutral, most straightforward order is:

• Η πορσελάνη είναι ακριβή.

But Greek word order is more flexible than English, so other orders are possible for emphasis, such as:

• Ακριβή είναι η πορσελάνη.

That said, for learners, the basic pattern
subject + είναι + adjective
is the safest one to use.