Η βαλβίδα είναι κλειστή.

Η is the definite article for a feminine singular noun in the nominative case. It means the.

So:

• η βαλβίδα = the valve

Greek articles change according to gender, number, and case, unlike English the, which stays the same.

In Greek, every noun has a grammatical gender: masculine, feminine, or neuter. Βαλβίδα is a feminine noun, so it takes feminine forms with articles and adjectives.

That is why you get:

• η βαλβίδα
• κλειστή and not κλειστός or κλειστό

Gender in Greek is a grammar feature, so it does not necessarily mean the object is biologically female.

Because adjectives in Greek must agree with the noun they describe.

Since βαλβίδα is:

• feminine
• singular
• nominative

the adjective must also be:

• feminine
• singular
• nominative

So:

• masculine: κλειστός
• feminine: κλειστή
• neuter: κλειστό

Here, κλειστή matches βαλβίδα.

Είναι means is here. It is the 3rd person singular present tense of είμαι = to be.

So:

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

In this sentence:

• Η βαλβίδα είναι κλειστή = The valve is closed

For a learner, the most useful way to treat κλειστή here is as an adjective meaning closed.

It is related to the verb κλείνω = to close, but in this sentence it functions like a normal adjective after είναι:

• Η πόρτα είναι κλειστή = The door is closed
• Η βαλβίδα είναι κλειστή = The valve is closed

So grammatically in practice, think of it as an adjective agreeing with the noun.

A simple pronunciation guide is:

• Η = ee
• βαλβίδα = val-VEE-tha
• είναι = EE-ne
• κλειστή = klee-STEE or more exactly kli-STEE

A few useful sound notes:

• β sounds like v in modern Greek
• δ sounds like th in this
• ει usually sounds like ee
• the stressed syllable is marked by the accent:
  • βαλβίδα
  • είναι
  • κλειστή

In a normal sentence like this, Greek usually keeps the verb είναι.

So the standard form is:

• Η βαλβίδα είναι κλειστή.

Leaving it out would sound incomplete in ordinary neutral Greek.

Greek can omit things in headlines, notes, or very informal contexts, but for learners, the safe rule is:

• use είναι in sentences like The valve is closed

Yes. Greek word order is more flexible than English, although the neutral order here is:

• Η βαλβίδα είναι κλειστή.

You may also hear:

• Κλειστή είναι η βαλβίδα.

That changes the focus/emphasis, not the basic meaning. It can sound like:

• It is the valve that is closed
• or The valve is closed with emphasis on closed

For learners, the original order is the best default.

In most normal situations, yes, that would sound unnatural if you mean the valve.

Greek uses the article very often, so:

• Η βαλβίδα είναι κλειστή = The valve is closed

If you wanted a valve, Greek would usually say:

• Μια βαλβίδα είναι κλειστή = A valve is closed

So in ordinary speech, do not drop the article here.

It is in the nominative singular.

Why?

Because βαλβίδα is the subject of the sentence, and subjects are normally in the nominative.

You can see this from the article too:

• η = feminine singular nominative

So:

• Η βαλβίδα = nominative singular subject

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

• Οι βαλβίδες είναι κλειστές.

Breakdown:

• οι = the
• βαλβίδες = valves
• είναι = are
• κλειστές = closed

Notice that είναι is used for both is and are in the present tense.

They are different meanings.

• Η βαλβίδα είναι κλειστή = The valve is closed
  This describes a state/condition.

• Η βαλβίδα κλείνει = The valve closes / is closing
  This describes an action or process.

So if you want to describe the valve’s current condition, είναι κλειστή is the right pattern.

Yes. Accent marks are important in Greek because they show which syllable is stressed.

In this sentence:

• βαλβίδα → stress on -βί-
• είναι → stress on εί-
• κλειστή → stress on -στή

Correct stress is an important part of sounding natural and being understood.