Ο ήχος ήταν τρομακτικός.

Ο is the masculine singular definite article, so it means the.

In this sentence:

• ο ήχος = the sound

Greek articles change for gender, number, and case, unlike English the, which always stays the same.

Here ο is used because ήχος is:

• masculine
• singular
• nominative (the subject of the sentence)

In Greek, every noun has a grammatical gender: masculine, feminine, or neuter.

Ήχος (sound) is simply a masculine noun. That is something you learn along with the word, just as you learn plural forms or pronunciation.

So you should ideally learn it as:

• ο ήχος = the sound

not just ήχος by itself.

That helps you remember:

• its gender
• which article it takes
• how adjectives must agree with it

Ήχος is pronounced roughly like EE-hos.

A more careful breakdown:

• ή = ee
• χ = a rough sound, like the ch in German Bach or Scottish loch
• ος = os

So the middle consonant is not like English h or k. It is the Greek letter χ, which has a throaty sound.

The stress is on the first syllable:

• Ήχος

Ήταν means was.

It is a past-tense form of the verb είμαι (to be).

So:

• είναι = is
• ήταν = was

In this sentence:

• Ο ήχος ήταν τρομακτικός.
• The sound was scary / frightening.

Grammatically, ήταν is the imperfect form of είμαι, but in many simple sentences like this, it is translated naturally as was.

Because the adjective has to agree with the noun it describes.

The noun is:

• ο ήχος
• masculine, singular, nominative

So the adjective must also be:

• masculine, singular, nominative

That gives:

• τρομακτικός

Compare:

• ο ήχος ήταν τρομακτικός = the sound was scary
• η φωνή ήταν τρομακτική = the voice was scary
• το θέαμα ήταν τρομακτικό = the sight was scary

Same adjective, different endings because of agreement.

Τρομακτικός means something like:

• scary
• frightening
• terrifying (depending on context)

It comes from the idea of causing fear or fright.

In everyday English, scary is often the most natural translation.
In a slightly more formal sense, frightening also fits very well.

So this sentence could be understood as:

• The sound was scary.
• The sound was frightening.

Because τρομακτικός is a predicate adjective, not part of a noun phrase like the scary sound.

Compare:

1. Ο τρομακτικός ήχος
   = the scary sound
   Here the adjective comes directly with the noun.

2. Ο ήχος ήταν τρομακτικός
   = the sound was scary
   Here the adjective comes after was and describes the subject.

English works the same way:

• the scary sound
• the sound was scary

You would not say the sound was the scary in English, and Greek works similarly here.

Both are in the nominative singular masculine.

Why?

• ήχος is the subject of the sentence, so it is nominative.
• τρομακτικός is linked to the subject through ήταν (was), so it also appears in the nominative as a predicate adjective.

So the pattern is:

• subject
  • to be
    • predicate adjective
• both subject and predicate adjective match in case, number, and gender

Yes, Greek word order is more flexible than English.

The most neutral order here is:

• Ο ήχος ήταν τρομακτικός.

But other orders are possible, especially for emphasis, such as:

• Τρομακτικός ήταν ο ήχος.

This can sound more emphatic, like:

• The sound was frightening.
• or even Frightening was the sound, in a more dramatic style

That said, for learners, the standard order subject + verb + complement is the safest and most natural pattern to use first.

The accent marks show which syllable is stressed.

In this sentence:

• ήχος → stress on the first syllable: Ήχος
• ήταν → stress on the first syllable: Ήταν
• τρομακτικός → stress on the last syllable: τρομακτικός

Greek spelling marks stress very consistently, which is very helpful for learners.

Note that Ο has no accent because it is a one-syllable article, and one-syllable words usually do not need a stress mark.

You may sometimes see variation in spelling with words related to τρομάζω / τρομάσσω, but the standard modern form you should learn here is:

• τρομακτικός

That is the normal adjective meaning scary / frightening.

So for a learner, the best form to use is:

• Ο ήχος ήταν τρομακτικός.

You would change ήταν (was) to είναι (is):

• Ο ήχος είναι τρομακτικός.
• The sound is scary.

So the pattern is:

• Ο ήχος είναι τρομακτικός. = present
• Ο ήχος ήταν τρομακτικός. = past

This is a useful pair to memorize.

Normally, you should include ο here.

• Ο ήχος ήταν τρομακτικός. = normal, natural Greek

Leaving out the article would usually sound unnatural in a basic sentence like this.

Greek uses the definite article more often than English in many contexts, and with a specific subject like the sound, the article is expected.

So for learners, the correct default is:

• ο ήχος

not just ήχος, unless you are using the word in a different structure or a very special style.