Η σύνθεση φαίνεται φυσική.

• Η = the (feminine singular nominative article)
• σύνθεση = composition / synthesis (feminine singular noun)
• φαίνεται = seems / appears / looks
• φυσική = natural (feminine singular adjective)

So the structure is:

The composition + seems + natural

Because σύνθεση is a feminine noun.

In Greek, the definite article changes for gender:

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

Since σύνθεση is feminine, it takes η:

• η σύνθεση

Because it has to agree with σύνθεση.

Greek adjectives agree with the noun they describe in:

• gender
• number
• case

Since σύνθεση is feminine singular nominative, the adjective must also be feminine singular nominative:

• masculine: φυσικός
• feminine: φυσική
• neuter: φυσικό

So:

• η σύνθεση φαίνεται φυσική not
• η σύνθεση φαίνεται φυσικός or
• η σύνθεση φαίνεται φυσικό

Φαίνεται is the 3rd person singular present form of φαίνομαι.

Here it means:

• seems
• appears
• sometimes looks

So η σύνθεση φαίνεται φυσική means the composition seems natural.

A useful thing to know: φαίνομαι has middle/passive-looking endings, but in meaning it is very often active-like: I seem / I appear, not necessarily I am appeared.

Because Greek has many verbs that use middle/passive forms but are translated actively in English.

So even though φαίνεται ends like a passive-form verb, here it simply means:

• it seems
• it appears

You should learn φαίνομαι as a normal vocabulary item meaning to seem / appear, rather than trying to force a passive translation every time.

Because φυσική is the complement of φαίνεται.

Compare in English:

• The composition is natural.
• The composition seems natural.

In the second sentence, you do not say seems is natural. Greek works the same way:

• είναι φυσική = is natural
• φαίνεται φυσική = seems natural

So no extra είναι is needed.

It can mean all three, depending on context.

In a sentence like this, seems is usually the most natural translation:

• Η σύνθεση φαίνεται φυσική = The composition seems natural

But in other contexts, appears or looks may fit better.

So it is best to think of φαίνεται as covering the general idea of seeming / appearing.

No. Φυσική can also be a noun meaning physics.

For example:

• Η φυσική είναι δύσκολη. = Physics is difficult.

But in Η σύνθεση φαίνεται φυσική, it is clearly an adjective, because it describes σύνθεση.

So here it means natural, not physics.

Yes. Greek word order is more flexible than English.

The most neutral order here is:

• Η σύνθεση φαίνεται φυσική.

But other orders are possible for emphasis, such as:

• Φυσική φαίνεται η σύνθεση.

That version puts more emphasis on φυσική.

Still, for learners, the original order is the safest and most natural starting point.

You add δεν before the verb:

• Η σύνθεση δεν φαίνεται φυσική.

This means:

• The composition doesn’t seem natural.

That is the normal way to negate a sentence with φαίνεται.

A rough pronunciation is:

ee SEEN-theh-see FEH-ne-teh fee-see-KEE

More closely in Modern Greek:

• Η = i
• σύνθεση = SIN-the-si
• φαίνεται = FE-ne-te
• φυσική = fi-si-KEE

A couple of useful pronunciation notes:

• αι is pronounced like e
• η is pronounced like ee
• θ is like th in think

So φαίνεται is pronounced more like FEnete, not fai-netai.