Η επιθυμία είναι δυνατή.

A good approximate pronunciation is:

ee e-pee-thee-MEE-a EE-ne thee-na-TEE

A few useful notes:

• Η = ee
• επιθυμία = e-pee-thee-MEE-a
• είναι = EE-ne
• δυνατή = thee-na-TEE if you approximate it with English sounds, but the first sound is actually δ, like the th in this

The accent marks show the stressed syllable:

• επιθυμία
• είναι
• δυνατή

Η is the feminine singular form of the definite article, so it means the.

In this sentence:

• Η επιθυμία = the desire

Greek articles change for gender, number, and case, so you do not use just one word for the in all situations.

Yes, επιθυμία is feminine.

You can tell because:

• it takes the feminine article η
• the adjective describing it is also feminine: δυνατή

Also, many Greek nouns ending in -ία are feminine, although that ending is a pattern, not an absolute rule for every word.

Because Greek adjectives must agree with the noun they describe in gender, number, and case.

Here:

• επιθυμία is feminine
• singular
• nominative

So the adjective must also be feminine singular nominative:

• masculine: δυνατός
• feminine: δυνατή
• neuter: δυνατό

That is why the sentence uses δυνατή.

είναι means is.

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

So the structure is:

• Η επιθυμία = the subject
• είναι = is
• δυνατή = possible / capable / strong, depending on context

In this sentence, είναι works just like is in English: it links the subject to a description.

Both are in the nominative singular feminine.

• Η επιθυμία is the subject, so nominative makes sense.
• δυνατή is a predicate adjective after είναι, and in Greek it agrees with the subject, so it is also nominative feminine singular.

So even though δυνατή comes after the verb, it still matches επιθυμία.

Because δυνατή is a predicate adjective, not part of the noun phrase.

Compare:

• Η επιθυμία είναι δυνατή. = The desire is possible.
• η δυνατή επιθυμία = the strong/possible desire depending on context

In the sentence you gave, δυνατή comes after είναι and describes the subject, so it normally does not take an article.

It can, depending on context.

The adjective δυνατός / δυνατή / δυνατό has a range of meanings, including ideas like:

• strong
• powerful
• capable
• possible

In expressions with είναι, Greek often uses this adjective with the sense of possible. Since the meaning has already been shown to the learner, that is the intended reading here.

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

The neutral order here is:

• Η επιθυμία είναι δυνατή.

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

• Δυνατή είναι η επιθυμία.

That does not automatically change the basic meaning, but it changes what is emphasized. For a learner, the original order is the safest and most neutral pattern.

Because Greek does not need a subject pronoun here.

The subject is already stated:

• Η επιθυμία

So Greek does not add a separate pronoun like it. In fact, Greek often leaves subject pronouns out unless they are needed for emphasis or contrast.

Greek often uses the definite article more freely than English, including with abstract nouns.

So Η επιθυμία can be perfectly normal where English might sometimes prefer just desire in a more general statement.

That means you should not expect article usage in Greek to match English exactly. Greek often sounds more natural with the article than a word-for-word English comparison would suggest.

The pattern is:

article + noun + form of to be + adjective

More specifically:

• Η = feminine singular definite article
• επιθυμία = feminine singular noun
• είναι = is
• δυνατή = feminine singular adjective agreeing with the noun

So this is a very common Greek sentence type: Subject + είναι + predicate adjective