Ακούσαμε έναν ασυνήθιστο ήχο.

Ακούσαμε means we heard.

It is the aorist form of ακούω (to hear / to listen to). In Modern Greek, the aorist usually describes a single completed action in the past.

So:

• ακούω = I hear / I listen
• άκουσα = I heard
• ακούσαμε = we heard

A useful comparison:

• Ακούγαμε = we were hearing / we used to hear
• Ακούσαμε = we heard (completed event)

So this sentence presents the hearing as one finished event.

Because Greek often doesn’t need subject pronouns when the verb ending already shows who the subject is.

Here, the ending -σαμε in Ακούσαμε tells you the subject is we.

So Greek can simply say:

• Ακούσαμε = we heard

If you added εμείς (we), it would usually sound emphatic or contrastive:

• Εμείς ακούσαμε έναν ασυνήθιστο ήχο.
  = We heard an unusual sound. (maybe not someone else)

Because ήχο is a masculine singular noun in the accusative case, and the indefinite article has to match it.

The forms are:

• ένας = a / one (masculine, nominative)
• έναν = a / one (masculine, accusative)
• ένα = a / one (neuter)

Since ήχος is masculine, Greek uses:

• έναν ήχο = a sound

Also, the final -ν in έναν is definitely kept here because the next word, ασυνήθιστο, begins with a vowel.

Because they are both in the masculine accusative singular.

This is very common in Greek.

Compare the nominative and accusative:

• ο ασυνήθιστος ήχος = the unusual sound
• έναν ασυνήθιστο ήχο = an unusual sound

So:

• ασυνήθιστος → ασυνήθιστο
• ήχος → ήχο

For many masculine nouns and adjectives, the accusative singular drops or changes the ending this way.

The dictionary form is ήχος.

That is the nominative singular form, the form you would usually look up in a dictionary.

So:

• ήχος = sound
• ήχο = sound (as a direct object)

In this sentence, ήχο is the direct object of Ακούσαμε, so it appears in the accusative.

ασυνήθιστο is an adjective meaning unusual.

It describes ήχο, so it has to agree with it in:

• gender: masculine
• number: singular
• case: accusative

That is why you get:

• έναν ασυνήθιστο ήχο

This is a good example of adjective agreement in Greek: the adjective changes form to match the noun it describes.

A good pronunciation guide is:

Ακούσαμε έναν ασυνήθιστο ήχο
[a-KOO-sa-me E-nan a-see-NEE-thee-sto EE-ho]

More accurately in IPA:

• Ακούσαμε = [aˈkusame]
• έναν = [ˈenan]
• ασυνήθιστο = [asiˈniθisto]
• ήχο = [ˈixo]

A few useful sound notes:

• ού sounds like oo in food
• θ sounds like th in thin
• χ in ήχο is not an English h; it is a rough sound like German Bach or Scottish loch
• the accent mark shows the stressed syllable:
  • ακούσαμε
  • ασυνήθιστο
  • ήχο

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

The sentence as written is neutral and natural:

• Ακούσαμε έναν ασυνήθιστο ήχο.

But Greek can move things around for emphasis, for example:

• Έναν ασυνήθιστο ήχο ακούσαμε.

This puts more focus on what we heard.

Even when the order changes, the endings and articles help show what each word is doing, so the meaning usually stays clear.

It can mean both, depending on context.

In this sentence, it clearly means hear:

• Ακούσαμε έναν ασυνήθιστο ήχο. = We heard an unusual sound.

But Greek also uses ακούω in the sense of listen to:

• Ακούω μουσική. = I listen to music.
• Άκουσέ με! = Listen to me!

So you should think of ακούω as a verb that covers both ideas, with the context telling you which meaning is intended.

It gives the word a negative sense, similar to English un- in unusual.

So:

• ασυνήθιστος = unusual / uncommon

This can help you remember the word: it has the same basic idea as English unusual.

Even if you do not analyze every part of the word, it is useful to notice that Greek often uses prefixes to create opposites, just as English does.