Η ταχύτητα σύνδεσης είναι μεγάλη.

• Η = the
• ταχύτητα = speed
• σύνδεσης = of connection / connection
• είναι = is
• μεγάλη = big, great, high

So the sentence literally means something like The speed of connection is great/high, and naturally in English this is The connection speed is high or The connection speed is fast.

Η is the feminine singular form of the definite article the.

Greek nouns have grammatical gender, so the article has to match the noun:

• ο for many masculine nouns
• η for many feminine nouns
• το for many neuter nouns

Since ταχύτητα is a feminine noun, it takes η:

• η ταχύτητα = the speed

Because grammatical gender in Greek is a property of the noun itself. It does not mean that speed is biologically female; it just belongs to the feminine grammatical class.

You usually have to learn a noun together with its article:

• η ταχύτητα
• η σύνδεση
• η ποιότητα

This helps you remember its gender and use adjectives correctly.

Because σύνδεσης is in the genitive case.

Greek often expresses X of Y by putting the second noun in the genitive:

• ταχύτητα σύνδεσης = speed of connection

The basic form is:

• η σύνδεση = the connection

Its genitive singular is:

• της σύνδεσης = of the connection

In this sentence, the article της is omitted because Greek often does that in this kind of noun phrase:

• ταχύτητα σύνδεσης = connection speed / speed of connection

Yes. English often puts one noun directly before another:

• connection speed
• internet speed
• download speed

Greek usually prefers a structure with the genitive:

• ταχύτητα σύνδεσης = connection speed
• literally speed of connection

So this is a very normal Greek way to build that kind of expression.

Because the adjective has to agree with the noun it describes.

The noun being described is η ταχύτητα, which is:

• feminine
• singular

So the adjective must also be feminine singular:

• masculine: μεγάλος
• feminine: μεγάλη
• neuter: μεγάλο

That is why Greek says:

• Η ταχύτητα είναι μεγάλη.

Because μεγάλη is a predicate adjective here, used after είναι (is).

Compare:

Attributive use:

• η μεγάλη ταχύτητα = the high/great speed

Predicate use:

• η ταχύτητα είναι μεγάλη = the speed is high/great

After είναι, Greek normally does not use the article with the adjective.

Yes, μεγάλη literally means big/great/large, but with speed Greek commonly uses big/high the way English says high speed.

So:

• μεγάλη ταχύτητα = high speed
• Η ταχύτητα σύνδεσης είναι μεγάλη = The connection speed is high

You could also see adjectives like γρήγορη (fast) in other contexts, but μεγάλη ταχύτητα is very natural Greek.

είναι means is here. It is the 3rd person singular form of the verb είμαι (to be) in the present tense.

Examples:

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

In this sentence:

• Η ταχύτητα σύνδεσης είναι μεγάλη.
• The connection speed is high.

A rough pronunciation guide is:

ee ta-KHEE-ta SYN-the-sis EE-ne me-GHA-lee

A few notes:

• η sounds like ee
• χύ in ταχύτητα has a sound like a soft throaty h/kh
• σύνδεσης has th as in this, not as in thin
• γ before α in μεγάλη is a voiced throaty sound, not an English hard g

A more learner-friendly approximation: ee ta-HEE-ta SEEN-dheh-sees EE-neh meh-GHA-lee

The written accent mark shows the stress:

• Η — no issue, it is just ee
• ταχύτητα → stress on χύ
• σύνδεσης → stress on σύν
• είναι → stress on εί
• μεγάλη → stress on γά

So the rhythm is roughly:

η τα-ΧΥ-τη-τα ΣΥΝ-δε-σης ΕΙ-ναι με-ΓΑ-λη

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

Neutral:

• Η ταχύτητα σύνδεσης είναι μεγάλη.

You might also hear a different order for emphasis, for example:

• Μεγάλη είναι η ταχύτητα σύνδεσης.

That sounds more marked, something like:

• The connection speed is high or even
• High is the connection speed

For most learners, the standard order is the safest one to use.

In normal standard Greek, that would usually sound incomplete or unnatural in this context.

Greek uses the definite article much more often than English does. So:

• Η ταχύτητα σύνδεσης είναι μεγάλη. = natural

If you remove Η, it no longer sounds like a normal complete statement about the connection speed.

Usually, yes, in context it would most naturally refer to something like a network or internet connection.

But grammatically, σύνδεση just means connection, so the phrase itself could refer to any kind of connection if the context made that clear.

In many real-life situations, though, a Greek speaker would understand:

• ταχύτητα σύνδεσης as connection speed / internet speed

Not exactly. It means the connection speed is high, not specifically download speed.

If you want download speed, Greek would normally use a different expression, such as:

• ταχύτητα λήψης = download speed

So:

• ταχύτητα σύνδεσης = connection speed
• ταχύτητα λήψης = download speed