Το κατάστρωμα είναι καθαρό.

Word by word:

• Το = the
• κατάστρωμα = deck
• είναι = is
• καθαρό = clean

So the structure is very close to English: The deck is clean.

Το is the definite article here, meaning the.

In this sentence:

• το = the for a neuter singular noun
• κατάστρωμα is a neuter singular noun

Greek articles change depending on gender, number, and case, so you cannot use just one form for all nouns the way English uses the.

Here, το κατάστρωμα means the deck.

Because Greek adjectives must agree with the noun they describe.

Since κατάστρωμα is:

• neuter
• singular

the adjective must also be neuter singular, so you get:

• καθαρός = masculine
• καθαρή = feminine
• καθαρό = neuter

So:

• ο διάδρομος είναι καθαρός = the corridor is clean
• η αίθουσα είναι καθαρή = the room/hall is clean
• το κατάστρωμα είναι καθαρό = the deck is clean

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

In this sentence it means is, but the same form is also used for:

• he is
• she is
• it is

So Greek does not have separate present forms like English am / is / are for every person in the same way. For the 3rd person singular, είναι is the normal form.

In a normal sentence like this, είναι is usually included:

• Το κατάστρωμα είναι καθαρό.

Greek can sometimes omit forms of to be in special contexts such as headlines, labels, notes, or very compressed speech, but for standard full sentences, learners should use είναι.

So if you want to say The deck is clean, the natural full sentence is:

• Το κατάστρωμα είναι καθαρό.

It is neuter.

A very common clue is the ending -μα, because many Greek nouns ending in -μα are neuter, for example:

• το γράμμα = the letter
• το όνομα = the name
• το πράγμα = the thing
• το κατάστρωμα = the deck

You can also tell from the article:

• το κατάστρωμα

The article το marks it as neuter singular.

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

In Το κατάστρωμα είναι καθαρό:

• το κατάστρωμα = the thing being talked about, so it is the subject
• καθαρό describes the subject

For neuter nouns like this, the nominative and accusative forms are often the same, so the form itself may not look different. But grammatically, here it is nominative.

A rough pronunciation guide is:

to ka-TA-stro-ma EE-ne ka-tha-RO

A few useful points:

• The stressed syllables are marked by the accent marks:
  • κατάστρωμα
  • είναι
  • καθαρό
• θ sounds like th in think
• αι in είναι is pronounced like e in modern Greek
• Greek ρ is usually a light rolled or tapped r

A rough transliteration is:

To katástroma íne katharó

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

The neutral order here is:

• Το κατάστρωμα είναι καθαρό.

But you may also hear different orders for emphasis, such as:

• Καθαρό είναι το κατάστρωμα.

That can sound like It’s the deck that is clean or put extra focus on clean or on the deck, depending on context.

For learners, the safest basic order is:

• subject + είναι + adjective

Usually no, not in normal standard Greek.

Greek uses the article much more often than English does. If you are talking about the deck, you normally say:

• Το κατάστρωμα είναι καθαρό.

Leaving out the article would usually sound unnatural here, unless it were some special context like a label, headline, or highly elliptical speech.

So for ordinary speech, keep the article.

Add δεν before the verb:

• Το κατάστρωμα δεν είναι καθαρό. = The deck is not clean.

This is the standard way to negate a present-tense sentence with είναι.

You need to change the noun, article, and adjective to the plural:

• Τα καταστρώματα είναι καθαρά.

Breakdown:

• τα = the (neuter plural)
• καταστρώματα = decks
• είναι = are / is
• καθαρά = clean (neuter plural)

Notice that είναι stays the same, but the article, noun, and adjective change to plural forms.

In this sentence, καθαρό is an adjective meaning clean.

More broadly, forms of καθαρός / καθαρή / καθαρό can also mean things like:

• clean
• clear
• pure

The exact meaning depends on context. Here, with deck, the natural meaning is simply clean.

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

English says:

• It is clean
• The deck is clean

Greek usually just uses the actual subject if it is stated:

• Το κατάστρωμα είναι καθαρό.

If the subject is already understood from context, Greek can also leave it out more easily than English. But here the noun το κατάστρωμα is the subject, so no extra it is needed.