Η αντικατάσταση κουφωμάτων είναι ενεργειακή παρέμβαση.

Η is the feminine singular definite article, meaning the.

It is used here because αντικατάσταση (replacement) is a feminine singular noun:

• η αντικατάσταση = the replacement

So the sentence begins with Η αντικατάσταση = The replacement.

Αντικατάσταση is a noun meaning replacement.

It comes from the verb αντικαθιστώ = to replace. Greek often forms action nouns from verbs, just like English does with pairs such as:

• to replace → replacement
• to intervene → intervention

So:

• αντικαθιστώ = I replace
• αντικατάσταση = replacement

It is a feminine noun, which is why it goes with η.

Κουφωμάτων is the genitive plural of κουφώματα.

Base form:

• το κούφωμα = frame / window or door frame
• τα κουφώματα = frames / window and door units

In this sentence, Greek uses the genitive to show what is being replaced:

• η αντικατάσταση κουφωμάτων = the replacement of frames / windows and doors

This is very common in Greek. Compare:

• η αγορά βιβλίων = the purchase of books
• η επισκευή σπιτιού = the repair of a house
• η αντικατάσταση κουφωμάτων = the replacement of frames/windows

So κουφωμάτων means of frames / of windows and doors.

Greek often leaves out the article in expressions like this, especially when a noun follows another noun and works almost like of ... in English.

So:

• η αντικατάσταση κουφωμάτων literally = the replacement of frames
• not necessarily the replacement of the frames

If Greek wanted to make it more specific, it could say:

• η αντικατάσταση των κουφωμάτων = the replacement of the frames / of the windows and doors

So the version without των is more general.

Κουφώματα is a practical building-related word. It usually refers to window and door frames, and often by extension the whole installed window/door units.

Depending on context, it may be translated as:

• frames
• window frames
• doors and windows
• window/door units
• joinery in technical or architectural contexts

In energy-efficiency contexts, αντικατάσταση κουφωμάτων usually means replacing old windows and doors with better-insulated ones.

Είναι means is.

It is the 3rd person singular form of είμαι = to be.

So:

• είναι = is

In this sentence:

• Η αντικατάσταση κουφωμάτων είναι ... = The replacement of windows/frames is ...

This is a straightforward subject + verb + complement sentence.

Ενεργειακή is the feminine singular form of the adjective ενεργειακός = energy-related / energetic / energy-efficiency-related, depending on context.

It has to agree with the noun it describes, which is παρέμβαση:

• παρέμβαση is feminine singular
• so the adjective must also be feminine singular
• therefore: ενεργειακή παρέμβαση

The main forms are:

• ενεργειακός = masculine
• ενεργειακή = feminine
• ενεργειακό = neuter

Literally, παρέμβαση means intervention.

But in technical, administrative, or policy language, it can also mean:

• measure
• action
• improvement
• works carried out

So ενεργειακή παρέμβαση is often best understood as:

• an energy-efficiency measure
• an energy-related intervention

A very literal translation would be energy intervention, but in natural English, energy-efficiency measure is often the best equivalent.

Because Modern Greek has no indefinite article.

English says:

• is an energy-efficiency measure

Greek simply says:

• είναι ενεργειακή παρέμβαση

Greek has:

• definite articles: ο, η, το = the
• but no separate word for a/an

So a bare singular noun after είναι can often correspond to a/an in English.

After είναι, Greek often uses the predicate noun without the definite article when it means a/an ... or when it is classifying something.

So:

• είναι ενεργειακή παρέμβαση = is an energy-related intervention / is an energy-efficiency measure

If you added the article:

• είναι η ενεργειακή παρέμβαση

that would usually mean something more like:

• it is the energy intervention which sounds much more specific and is not what this sentence is doing.

Here the sentence is classifying the subject, not identifying it as one unique specific thing.

The structure is:

• Η αντικατάσταση κουφωμάτων = subject noun phrase
• είναι = verb
• ενεργειακή παρέμβαση = predicate noun phrase / complement

So:

[Subject] + [is] + [classification]

More literally:

• The replacement of frames/windows is an energy-related intervention

This is a very common Greek sentence pattern.

Yes, Greek word order is more flexible than English, although the original order is the most neutral here.

The standard version:

• Η αντικατάσταση κουφωμάτων είναι ενεργειακή παρέμβαση.

You could also move things around for emphasis, for example:

• Ενεργειακή παρέμβαση είναι η αντικατάσταση κουφωμάτων.

That would sound more like:

• The replacement of windows is an energy-efficiency measure with stronger focus on ενεργειακή παρέμβαση.

So yes, word order can change, but the original sentence is the most natural neutral phrasing.

A rough pronunciation guide is:

i andikaTÁstasi koufoMÁton Íne eneryiakÍ paremVAsi

A few helpful notes:

• Η sounds like ee
• αι in είναι sounds like e
• ω and ο are both pronounced o in Modern Greek
• stress matters a lot in Greek:
  • αντικατάσταση
  • κουφωμάτων
  • είναι
  • ενεργειακή
  • παρέμβαση

If you want to sound natural, pay special attention to the stressed syllables.