Η πισίνα είναι ανοιχτή.

• Η = the feminine singular definite article, the
• πισίνα = pool, a feminine singular noun
• είναι = is, from the verb είμαι (to be)
• ανοιχτή = open, a feminine singular adjective

So the structure is:

article + noun + is + adjective

Very similar to English: The pool is open.

Because Greek usually uses a definite article where English uses the.

Here, πισίνα is a feminine singular noun, so its article is η.

Some common singular definite articles are:

• ο for masculine
• η for feminine
• το for neuter

So:

• η πισίνα = the pool

Because adjectives in Greek normally agree with the noun they describe in:

• gender
• number
• case

Since πισίνα is feminine singular, the adjective must also be feminine singular:

• ανοιχτός = masculine
• ανοιχτή = feminine
• ανοιχτό = neuter

So Greek says, in effect, the pool is open-feminine, because pool is a feminine noun.

Because this sentence uses the adjective as a predicate adjective after είναι:

• Η πισίνα είναι ανοιχτή.
• The pool is open.

In this kind of sentence, the adjective is in the nominative, matching the subject η πισίνα.

You would see other endings in other grammatical contexts, but here the basic nominative feminine singular form ανοιχτή is the correct one.

In standard Greek, είναι is normally kept here.

So the natural full sentence is:

• Η πισίνα είναι ανοιχτή.

In some informal contexts, Greek can occasionally omit forms of to be, especially in headlines, notes, or very casual speech, but for learners you should treat είναι as necessary in normal sentences like this.

Yes, Greek word order is more flexible than English, although Η πισίνα είναι ανοιχτή is the most neutral order.

You may also hear:

• Ανοιχτή είναι η πισίνα.
• Η πισίνα ανοιχτή είναι. (less neutral, more marked)

Changing the order usually changes the emphasis, not the core meaning.

For everyday use, stick with:

• Η πισίνα είναι ανοιχτή.

A simple learner-friendly pronunciation is:

ee pee-SEE-na EE-ne a-neekh-TEE

A few notes:

• η sounds like ee
• πί in πισίνα is stressed? Actually the stress is on σί: πι-SEE-na
• είναι is usually pronounced roughly EE-ne
• χτ in ανοιχτή can be tricky; the χ is like a throaty sound, somewhat like German Bach
• The stress in ανοιχτή is on the last syllable: a-noi-khTEE

Greek uses an accent mark to show the stressed syllable, but monosyllabic words usually do not take an accent.

So:

• η = no accent, because it is one syllable
• πισίνα = accent on σί
• είναι = accent on εί
• ανοιχτή = accent on τή

A very common beginner confusion is:

• η = the (feminine article)
• ή = or

That accent changes the word.

Not quite. You may also see ανοικτή.

So both of these are possible:

• Η πισίνα είναι ανοιχτή.
• Η πισίνα είναι ανοικτή.

They both mean The pool is open.

In everyday Modern Greek, ανοιχτή is very common in speech. Ανοικτή is also correct and may sound a bit more formal or more standard in some contexts.

You add δεν before the verb:

• Η πισίνα δεν είναι ανοιχτή.

Pattern:

• είναι = is
• δεν είναι = is not

So δεν is the basic negation word used before the verb in statements.

You would make the article, noun, and adjective plural:

• Οι πισίνες είναι ανοιχτές.
• The pools are open.

Compare:

• singular: Η πισίνα είναι ανοιχτή.
• plural: Οι πισίνες είναι ανοιχτές.

Notice the changes:

• η → οι
• πισίνα → πισίνες
• ανοιχτή → ανοιχτές

The verb είναι stays the same in singular and plural.

It can mean both, depending on context.

With places, shops, services, and facilities, ανοιχτός / ανοιχτή / ανοιχτό often means:

• open
• open for business
• available for use

So with πισίνα, Η πισίνα είναι ανοιχτή naturally means the pool is open and available, not just that some door or gate is physically open.

Greek often uses the same adjective for both ideas, just like English does.