Το μπουφάν είναι αδιάβροχο.

• Το = the (neuter singular definite article)
• μπουφάν = jacket
• είναι = is
• αδιάβροχο = waterproof

So the structure is:

Το μπουφάν = the jacket
είναι = is
αδιάβροχο = waterproof

A very literal word-for-word version is The jacket is waterproof.

Το is the definite article, meaning the.

Greek articles change according to gender, number, and case. Here, μπουφάν is a neuter singular noun, so the article is το.

Compare:

• ο = masculine singular the
• η = feminine singular the
• το = neuter singular the

So το μπουφάν means the jacket.

Because in Greek, every noun has a grammatical gender: masculine, feminine, or neuter.
Μπουφάν happens to be neuter: το μπουφάν.

This is grammatical gender, not biological gender. A jacket is not “male” or “female”; Greek just assigns the noun to a gender class.

Also, μπουφάν is a loanword and is commonly treated as indeclinable and neuter.

Because it agrees with μπουφάν.

In Greek, adjectives usually agree with the noun they describe in:

• gender
• number
• case

Since μπουφάν is neuter singular, the adjective is also neuter singular:

• masculine: αδιάβροχος
• feminine: αδιάβροχη
• neuter: αδιάβροχο

So:

• το μπουφάν είναι αδιάβροχο
• η τσάντα είναι αδιάβροχη
• ο σάκος είναι αδιάβροχος

Είναι is the 3rd person singular form of είμαι, meaning to be.

Here it means is:

• είμαι = I am
• είσαι = you are
• είναι = he/she/it is

So in this sentence:

• Το μπουφάν είναι αδιάβροχο = The jacket is waterproof

Also, είναι is the same form for they are in Modern Greek, so context tells you whether it means is or are.

In this sentence, yes: it is an adjective meaning waterproof.

But αδιάβροχο can also be used as a noun in Greek, meaning raincoat.

So:

• Το μπουφάν είναι αδιάβροχο = The jacket is waterproof
• Το αδιάβροχο = the raincoat

Context tells you which meaning is intended.

A rough pronunciation guide is:

To bou-FAN EE-ne a-DHYAV-ro-ho

More approximately:

• Το = to
• μπουφάν = boo-FAN
• είναι = EE-ne
• αδιάβροχο = a-DHYAV-ro-ho

A few useful pronunciation notes:

• μπ at the beginning of a word is usually pronounced like b
• ει sounds like ee
• δ sounds like th in this
• χ is a throaty sound, like German Bach or Scottish loch

Yes, Greek word order is more flexible than English, though the basic order here is the most neutral and natural:

Το μπουφάν είναι αδιάβροχο.

You may also hear:

• Αδιάβροχο είναι το μπουφάν.

That version gives more emphasis to αδιάβροχο.

Still, for learners, the normal pattern subject + είναι + adjective is the safest choice.

Usually μπουφάν stays the same, because it is commonly treated as an indeclinable noun.

So you often get:

• το μπουφάν = the jacket
• τα μπουφάν = the jackets

What changes is mainly the article, not the noun itself.

This is common with some borrowed words in Greek.

It is in the nominative, because it is the subject of the sentence.

The sentence says something about the jacket:

• The jacket is waterproof.

The adjective αδιάβροχο is also in the nominative, because predicate adjectives in Greek agree with the subject.

One small detail: with neuter singular nouns like this, το looks the same in both nominative and accusative, so the form itself does not show the difference clearly here. The sentence structure tells you it is nominative.

You would normally use the indefinite article:

Ένα μπουφάν είναι αδιάβροχο.

That means A jacket is waterproof or One jacket is waterproof, depending on context.

So:

• το μπουφάν = the jacket
• ένα μπουφάν = a jacket

Greek does have an indefinite article, unlike some languages.

You would put the adjective with the noun, not after είναι:

το αδιάβροχο μπουφάν

That means the waterproof jacket.

So compare:

• Το μπουφάν είναι αδιάβροχο. = The jacket is waterproof.
• Το αδιάβροχο μπουφάν. = The waterproof jacket.

This is an important difference:

• after είναι: the adjective is part of the statement
• before the noun: the adjective directly describes the noun

Yes. It is completely natural and standard Greek.

It sounds like a normal descriptive sentence someone might say in everyday life, for example when talking about clothes, outdoor gear, or shopping.

So as a model sentence, it is very useful because it shows a basic and common pattern:

article + noun + είναι + adjective