Η υπογραφή είναι ψεύτικη.

Η is the feminine singular definite article in Greek, meaning the.

It is used because υπογραφή (signature) is a feminine singular noun.

So:

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

In this sentence, Η υπογραφή means the signature.

In Greek, every noun has a grammatical gender: masculine, feminine, or neuter.
Υπογραφή happens to be a feminine noun, so it takes:

• the feminine article η
• a feminine form of the adjective: ψεύτικη

This is grammatical gender, not natural gender. A thing like a signature can still be grammatically feminine.

Because adjectives in Greek must agree with the noun they describe in:

• gender
• number
• case

Here, υπογραφή is:

• feminine
• singular
• nominative

So the adjective must also be feminine singular nominative:

• masculine: ψεύτικος
• feminine: ψεύτικη
• neuter: ψεύτικο

That is why the sentence uses ψεύτικη.

Είναι means is here.

It is the 3rd person singular form of the verb είμαι (to be).

Greek verbs do not change to match grammatical gender in this kind of sentence.
So είναι is the same whether the subject is masculine, feminine, or neuter:

• Ο άντρας είναι... = The man is...
• Η υπογραφή είναι... = The signature is...
• Το παιδί είναι... = The child is...

The adjective changes for gender, but the verb είναι does not.

Greek usually does not need a separate subject pronoun like it when the subject noun is already stated.

In English, you might think of the structure as:

• The signature is fake.

Greek says exactly that:

• Η υπογραφή είναι ψεύτικη.

There is no need to add a separate word for it, because Η υπογραφή already tells you the subject.

The most neutral word order here is:

• Η υπογραφή είναι ψεύτικη.

This is the normal equivalent of The signature is fake.

Greek word order is somewhat flexible, so other orders are possible for emphasis, for example:

• Ψεύτικη είναι η υπογραφή. = It’s the signature that is fake / The signature is fake with emphasis
• Είναι ψεύτικη η υπογραφή. = also possible, depending on context

But for a learner, the standard pattern to remember is:

• article + noun + είναι + adjective

Yes, but then the meaning is slightly different in structure.

• Η υπογραφή είναι ψεύτικη. = The signature is fake.
• Η ψεύτικη υπογραφή = the fake signature

So:

• after είναι, it is a predicate adjective: is fake
• before the noun, it is an attributive adjective: fake signature

Both are correct, but they are used in different sentence patterns.

A natural pronunciation is approximately:

ee ee-po-gra-FEE EE-ne PSEF-tee-hee

A more careful breakdown:

• Η = ee
• υπογραφή = ee-po-gra-FEE
• είναι = EE-ne
• ψεύτικη = PSEF-tee-hee

A few helpful notes:

• υ here sounds like ee
• γρ in υπογραφή is like gr
• ψ is pronounced ps, as in lapse
• χ in ψεύτικη is a rough h-like sound, not an English k

The accent marks show which syllable is stressed.

In this sentence:

• υπογραφή → stress on the last syllable: υπογραφή
• είναι → stress on the first syllable: είναι
• ψεύτικη → stress on the first syllable: ψεύτικη

Stress matters in Greek pronunciation, so it is important to learn words together with their written accents.

No. Ψεύτικη is a common everyday word for fake, false, or not genuine.

But in some contexts, Greek might also use πλαστή for something forged or counterfeit, especially in more formal or legal language.

So depending on context:

• Η υπογραφή είναι ψεύτικη. = The signature is fake.
• Η υπογραφή είναι πλαστή. = The signature is forged / counterfeit.

A learner will often meet ψεύτικος / ψεύτικη / ψεύτικο first, because it is a very common adjective.

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

The basic structure is:

• Η υπογραφή = subject
• είναι = verb
• ψεύτικη = predicate adjective

So both Η and υπογραφή are in the nominative feminine singular, and the adjective ψεύτικη matches that.

Sometimes Greek can omit the article, but in this sentence Η υπογραφή είναι ψεύτικη is the normal and natural version if you mean the signature is fake.

If you say:

• Υπογραφή είναι ψεύτικη

that sounds incomplete or unnatural in ordinary Greek.

If you wanted to say A signature is fake, Greek would usually restructure the sentence rather than simply dropping the article in a direct English-like way.

So for this sentence, keep the article:

• Η υπογραφή είναι ψεύτικη.