Learn Hardcore Greek: Ο έκτος όροφος είναι ήσυχος.

Ο έκτος όροφος – the subject (nominative): “the sixth floor”
- Ο – definite article (masc. nom. sg.)
- έκτος – ordinal number used as an adjective (masc. nom. sg.)
- όροφος – noun (masc. nom. sg.)
είναι – verb “is” (3rd person singular of είμαι)
ήσυχος – predicate adjective “quiet” (masc. nom. sg.), describing όροφος.

So the structure is: [Subject] [is] [adjective] = “The sixth floor is quiet.”

Why do we say έκτος and not έξι for “sixth”?

έξι is the cardinal number “six.”
έκτος is the ordinal number “sixth.”

In Greek, ordinal numbers behave like adjectives and must agree with the noun in:

gender: έκτος (masc.), έκτη (fem.), έκτο (neut.)
number and case as well.

So:

Ο έκτος όροφος – the sixth floor (masc.)
Η έκτη μέρα – the sixth day (fem.)
Το έκτο βιβλίο – the sixth book (neut.)

In this sentence, όροφος is masculine, so we use έκτος.

Why does ήσυχος end in -ος? Why not ήσυχο?

ήσυχος is an adjective that must agree with the noun it describes (όροφος) in gender, number, and case.

όροφος is masculine, singular, nominative.
Therefore the adjective is also masculine, singular, nominative: ήσυχος.

Other forms of the adjective:

Masculine: ήσυχος (nom. sg.), ήσυχοι (nom. pl.)
Feminine: ήσυχη, ήσυχες
Neuter: ήσυχο, ήσυχα

If the noun were neuter, we would use ήσυχο:

Το δωμάτιο είναι ήσυχο. – The room is quiet.

Why does the adjective έκτος come before the noun όροφος? Could it come after?

The normal, neutral order for an adjective that directly describes a noun is:

article + adjective + noun
Ο έκτος όροφος

You can also find όροφος έκτος, but that sounds more like a label or technical specification (e.g., in a list, announcement, or when contrasting several floors). In everyday neutral speech, Ο έκτος όροφος is the usual order.

So:

Ο έκτος όροφος είναι ήσυχος. – fully natural, neutral statement
Ο όροφος έκτος είναι ήσυχος. – possible, but marked or stylistic.

Could the word order around είναι be different, like Ο έκτος όροφος ήσυχος είναι?

Greek word order is more flexible than English, but there is still a most natural order.

Ο έκτος όροφος είναι ήσυχος. – normal, neutral.
Ο έκτος όροφος ήσυχος είναι. – possible, but sounds poetic or very emphatic (e.g., stressing ήσυχος).
Ήσυχος είναι ο έκτος όροφος. – puts emphasis first on ήσυχος (“Quiet is the sixth floor”).

For everyday speech, you should keep Ο έκτος όροφος είναι ήσυχος.

Can I drop είναι and just say Ο έκτος όροφος ήσυχος?

In normal sentences, Greek usually keeps the verb είναι.

Ο έκτος όροφος είναι ήσυχος. – standard, correct sentence.

You might see είναι omitted in:

headlines,
notes, signs, labels,
telegraphic/very informal style.

For a learner, it’s better to always include είναι in full sentences.

Is the article Ο really necessary? Could I say Έκτος όροφος είναι ήσυχος?

You can find the article dropped in:

floor labels: 6ος όροφος – ήσυχος,
very short notes, lists, timetables.

But in ordinary spoken or written Greek, when you make a full statement, you normally use the definite article with specific, known things:

Ο έκτος όροφος είναι ήσυχος. – natural, standard.
Έκτος όροφος είναι ήσυχος. – sounds like a heading, label, or fragment.

So yes, for normal speech, keep Ο.

What exactly does όροφος mean? Is it the same as “floor” in all senses?

όροφος means “storey / level of a building” (first floor, second floor, etc.), not the surface you walk on inside a room.

Examples:

Ποιος όροφος; – Which floor (which storey)?
Μένω στον πέμπτο όροφο. – I live on the fifth floor.

For the floor surface (what you walk on), Greeks more often say:

πάτωμα – the floor (surface of a room).

So Ο έκτος όροφος είναι ήσυχος. refers to the sixth storey, not the physical ground inside a room.

What case is used for Ο έκτος όροφος and ήσυχος, and why?

Both Ο έκτος όροφος and ήσυχος are in the nominative singular masculine.

The subject of a sentence is in the nominative: Ο έκτος όροφος.
An adjective that renames or describes the subject via “to be” (a predicate adjective) also appears in the nominative:
- ήσυχος agrees with όροφος in gender, number, and case.

So you have:

Subject: Ο έκτος όροφος (nom.)
Verb: είναι
Predicate adjective: ήσυχος (nom.)

How do you pronounce the sentence?

A simple phonetic approximation (using English-like spelling) is:

Ο – “o” as in more (shorter)
έκτος – ÉK-tos (stress on έκ)
όροφος – Ó-ro-fos (stress on ό)
είναι – Í-ne (two syllables: EE-neh)
ήσυχος – Í-si-hos (stress on ή, “h” as in he, Greek χ is like a soft “kh” in the back of the mouth)

With stress marked:

Ο ÉKTOS Órofos Íne Ísihos.

In IPA:

/o ˈektos ˈorofos ˈine ˈisixos/

Does ήσυχος only mean “quiet,” or can it also describe a person as “calm”?

ήσυχος can describe both:

Places / situations: quiet, not noisy
- Η γειτονιά είναι ήσυχη. – The neighborhood is quiet.
People: quiet, calm, not troublesome
- Είναι πολύ ήσυχος μαθητής. – He is a very quiet / well-behaved student.

So in Ο έκτος όροφος είναι ήσυχος., it means the sixth floor is quiet (not noisy).