Ο σκύλος γαβγίζει μόνο όταν κάποιος χτυπάει το κουδούνι.

Ο is the masculine singular nominative form of the definite article, so here it means the.

It matches σκύλος because σκύλος is:

• masculine
• singular
• the subject of the sentence

So Ο σκύλος = the dog.

σκύλος is the basic singular form of the noun dog when it is the subject of the sentence.

Greek changes noun endings depending on grammatical role. Here the dog is doing the action, so Greek uses the nominative form:

• ο σκύλος = the dog (subject)
• τον σκύλο = the dog (object)

In this sentence, the dog is the one barking, so σκύλος is correct.

Not necessarily.

Greek nouns have grammatical gender, and σκύλος is a masculine noun. In many contexts, ο σκύλος can simply mean the dog, even if the animal’s biological sex is not important.

If you specifically wanted to say female dog, Greek can use η σκύλα, but ο σκύλος is very common as the general word for dog.

γαβγίζει is the 3rd person singular present tense of γαβγίζω = to bark.

So:

• γαβγίζω = I bark / I am barking
• γαβγίζει = he/she/it barks / is barking

Because the subject is ο σκύλος, Greek uses the 3rd person singular form.

Greek often uses the present tense for:

• general truths
• habits
• repeated actions

So Ο σκύλος γαβγίζει μόνο όταν κάποιος χτυπάει το κουδούνι describes a usual pattern, not just one event happening right now.

In English, we do the same:

• The dog barks only when someone rings the doorbell.

μόνο means only, and όταν means when.

Together, μόνο όταν means only when.

It limits the situation in which the dog barks:

• the dog does not bark all the time
• it barks only in the case that someone rings the doorbell

So μόνο is modifying the whole when-clause.

όταν means when, but in sentences about repeated or habitual actions, it often has the sense of whenever.

So this sentence can be understood as:

• The dog barks only when someone rings the doorbell
• or more naturally in context, The dog only barks whenever someone rings the doorbell

Greek uses όταν for both kinds of meaning, and the broader context tells you whether it is one event or a repeated pattern.

κάποιος means someone or somebody.

It is an indefinite pronoun. Here it is the subject of χτυπάει, so it is in the nominative form.

Compare:

• κάποιος = someone (subject)
• κάποιον = someone (object)

In this sentence, someone is the person doing the action of ringing/pressing the doorbell, so κάποιος is correct.

Yes. χτυπάει and χτυπά are both common forms of the 3rd person singular present of χτυπάω / χτυπώ.

So both can mean:

• he/she/it hits
• he/she/it rings
• he/she/it knocks
• he/she/it presses
  depending on context

In everyday Greek, χτυπάει is very common and natural.

So:

• κάποιος χτυπάει το κουδούνι
• κάποιος χτυπά το κουδούνι

are both acceptable.

Literally, χτυπάω / χτυπώ can mean hit or strike, but very often it is used more idiomatically.

With το κουδούνι, it means something like:

• rings the doorbell
• presses the doorbell
• sometimes knocks the bell in a more literal older sense

So although the basic verb can mean hit, in this sentence you should understand it as ringing/pressing the doorbell.

Greek often uses the definite article more regularly than English does.

So where English may say:

• someone rings the doorbell

Greek very naturally says:

• κάποιος χτυπάει το κουδούνι

The article το is the neuter singular definite article, agreeing with κουδούνι.

Also, κουδούνι is a neuter noun, so:

• το κουδούνι = the bell / the doorbell

Good question. κουδούνι is a neuter noun, and in the singular, many neuter nouns have the same form in the nominative and accusative.

So:

• το κουδούνι = the bell (subject form)
• το κουδούνι = the bell (object form)

The article also stays το in both nominative and accusative singular for neuter nouns.

That is why it looks unchanged even though it is the direct object here.

The sentence uses a very normal Greek word order:

• Ο σκύλος = subject
• γαβγίζει = verb
• μόνο όταν... = adverbial clause

So the structure is roughly:

The dog barks only when someone rings the doorbell.

Greek word order is fairly flexible, but this version sounds natural and neutral.

For example, you could also say:

Ο σκύλος γαβγίζει όταν κάποιος χτυπάει το κουδούνι.

That means The dog barks when someone rings the doorbell, but without the strong restriction of μόνο.

Yes, absolutely.

You could say:

Όταν κάποιος χτυπάει το κουδούνι, ο σκύλος γαβγίζει.

That means: When someone rings the doorbell, the dog barks.

If you want to keep the meaning only when, you could say:

Ο σκύλος γαβγίζει μόνο όταν κάποιος χτυπάει το κουδούνι.

That version keeps the focus on the limitation: the dog barks only in that situation.

So changing the order is possible, but it can slightly change what feels most emphasized.

A simple pronunciation guide is:

O SKEE-los gav-GHEE-zee MO-no OH-tan KA-po-yos htee-PA-ee to koo-THOO-nee

A few helpful notes:

• σκ in σκύλος sounds like sk
• γ before front vowels can sound soft, like a voiced version of y or a soft gh
• χ in χτυπάει is a throaty sound, not like English ch
• the stressed syllables are marked by the written accents:
  • σκύλος
  • γαβγίζει
  • μόνο
  • όταν
  • κάποιος
  • χτυπάει
  • κουδούνι

Most naturally, it describes a general habit or repeated situation.

That is because:

• both verbs are in the present tense
• the sentence sounds like a general statement about the dog’s behavior

So the idea is:

• As a rule, the dog only barks when someone rings the doorbell.

If you wanted to talk about one specific past event, Greek would use different tense forms.