Ο ανάδοχος μιλάει με τον κτηνίατρο.

A useful approximation is:

o a-NA-tho-hos mi-LA-i me ton kti-NIA-tro

A few sound notes:

• δ in ανάδοχος sounds like th in this
• χ sounds like a rough h/ch, like in Scottish loch
• κτ in κτηνίατρο is pronounced as a cluster: kt
• the written accent shows the stressed syllable:
  • ανάδοχος
  • μιλάει
  • κτηνίατρο

So the stress is on NA, LA, and NIA.

Because they are in different grammatical roles.

• ο ανάδοχος is the subject of the sentence, so it is in the nominative
• τον κτηνίατρο comes after με, and in Modern Greek με takes the accusative

So:

• nominative masculine singular article: ο
• accusative masculine singular article: τον

That is why the sentence uses ο ανάδοχος but τον κτηνίατρο.

This is a very common pattern with masculine nouns ending in -ος.

For many of these nouns:

• nominative singular: -ος
• accusative singular: -ο

So:

• ο κτηνίατρος = the veterinarian/vet
• τον κτηνίατρο = the veterinarian/vet

The final -ς drops in the accusative singular.

μιλάει is the present tense, third person singular form of μιλάω / μιλώ, meaning to speak / to talk.

So μιλάει means:

• he/she talks
• he/she is talking
• it talks / is talking if the subject is not a person

In this sentence, it agrees with the singular subject ο ανάδοχος.

Yes, in everyday Modern Greek they are both standard and mean the same thing here.

So these are both possible:

• Ο ανάδοχος μιλάει με τον κτηνίατρο.
• Ο ανάδοχος μιλά με τον κτηνίατρο.

The version with μιλάει may sound a little fuller or slightly more conversational to some speakers, but both are normal.

Literally, με usually means with, but with verbs like μιλάω / μιλώ, Greek often uses με where English might say either:

• talk with
• talk to
• speak with
• speak to

So μιλάει με τον κτηνίατρο can correspond naturally to English is talking with the veterinarian or is talking to the veterinarian.

Greek and English do not always choose the same preposition.

Yes, in Modern Greek με is followed by the accusative.

Examples:

• με τον κτηνίατρο
• με τη φίλη
• με το παιδί

This is why κτηνίατρος appears as κτηνίατρο after με.

Yes. Greek word order is more flexible than English.

The sentence:

Ο ανάδοχος μιλάει με τον κτηνίατρο.

is a neutral, straightforward order.

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

• Με τον κτηνίατρο μιλάει ο ανάδοχος.

That could put more focus on with the veterinarian.

Because Greek marks grammatical relationships with articles and endings, word order is not as rigid as in English. Still, the original version is the most neutral and natural for a learner to use first.

Usually yes, if you mean specific people.

• ο ανάδοχος = the sponsor/contractor/godparent/etc. depending on context
• τον κτηνίατρο = the veterinarian

If you remove the article before κτηνίατρο, the meaning changes:

• με τον κτηνίατρο = with the veterinarian
• με κτηνίατρο = with a veterinarian

So the articles matter.

In this sentence it is masculine, because the article is ο.

But ανάδοχος can often be used as a common-gender noun, meaning the noun form stays the same and the article shows the gender:

• ο ανάδοχος = masculine
• η ανάδοχος = feminine

So if the person were female, you could say:

• Η ανάδοχος μιλάει με τον κτηνίατρο.

The verb μιλάει does not change for gender.

Because the masculine accusative article is τον, and in standard Greek the final -ν is kept before certain sounds, including κ.

So:

• τον κτηνίατρο is the expected form

This final -ν helps the phrase sound smoother and is standard here.