Η δωρεά είναι έτοιμη.

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

In this sentence, η δωρεά = the donation.

Greek articles change for gender, number, and case, so you cannot always use the same form of the.

In Greek, every noun has a grammatical gender: masculine, feminine, or neuter.
Δωρεά is a feminine noun, which is why it takes:

• the feminine article η
• the feminine adjective form έτοιμη

So the sentence agrees all the way through:

• Η = feminine article
• δωρεά = feminine noun
• έτοιμη = feminine adjective

Είναι means is here.

It is the present-tense form of the verb είμαι = to be.

In this sentence:

• Η δωρεά = the donation
• είναι = is
• έτοιμη = ready

So the structure is very close to English:
The donation is ready.

Because Greek adjectives must agree with the noun they describe.

Since δωρεά is:

• feminine
• singular
• nominative

the adjective also has to be feminine singular nominative:

• masculine: έτοιμος
• feminine: έτοιμη
• neuter: έτοιμο

So:

• Ο άντρας είναι έτοιμος. = The man is ready.
• Η δωρεά είναι έτοιμη. = The donation is ready.
• Το δώρο είναι έτοιμο. = The gift is ready.

It is an adjective.

It describes the noun δωρεά and works as a predicate adjective after είναι.

So Greek is doing the same kind of thing as English in The donation is ready.

The accent mark in Greek shows which syllable is stressed.

• δωρεά is stressed at the end: do-re-A
• έτοιμη is stressed near the beginning: E-ti-mi
• είναι is stressed on the first part: I-ne

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

A rough pronunciation of the whole sentence is:

ee tho-re-A EE-ne E-ti-mee

A simple learner-friendly pronunciation is:

ee tho-re-A EE-ne E-ti-mee

A slightly more careful breakdown:

• Η → ee
• δωρεά → tho-re-A
• είναι → EE-ne
• έτοιμη → E-ti-mee

Notes:

• δ in Modern Greek sounds like th in this, not like English d
• η, ει, and οι often sound like ee
• the capitalized part above shows the stressed syllable

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

The neutral, standard order is:

Η δωρεά είναι έτοιμη.

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

• Έτοιμη είναι η δωρεά.
  = The donation is ready / Ready is the donation
  This puts extra focus on ready.

Even so, the original sentence is the most straightforward version for a learner.

Usually yes, if you mean the donation.

Greek uses the definite article very often, and in this sentence η δωρεά is the normal way to say the donation.

If you removed the article and said Δωρεά είναι έτοιμη, it would sound unnatural or incomplete in normal Greek.

If you wanted a donation, you would need an indefinite expression such as:

• Μια δωρεά είναι έτοιμη. = A donation is ready.

Both are in the nominative singular feminine.

• Η δωρεά is nominative because it is the subject
• έτοιμη is also nominative because it agrees with the subject as a predicate adjective after είναι

This is common in Greek: after to be, the describing adjective matches the subject.

Yes, depending on context, δωρεά can refer to a donation, a gift, or something given free of charge in a more formal sense.

But in many everyday contexts, donation is the safest meaning.

So if the meaning has already been given to the learner, it makes sense to read this sentence as:

The donation is ready.

Not only that. Είναι is used for both:

• third person singular = he/she/it is
• third person plural = they are

So Greek uses the same form in both cases.

Here it clearly means is, because the subject η δωρεά is singular.

Because Greek normally does not need a subject pronoun when the subject is already stated.

The noun itself, η δωρεά, is the subject, so there is no need to add a separate word for it.

Greek often avoids unnecessary pronouns, much more than English does.