Η υιοθεσία γίνεται σήμερα.

Because υιοθεσία is a feminine singular noun, and in Greek nouns normally take a definite article when you are talking about a specific event or thing.
So η is the feminine singular nominative definite article, roughly corresponding to the.

• η υιοθεσία = the adoption

Greek uses articles more often than English does, so keeping the article here sounds natural.

It is in the nominative singular.

You can tell because it is the subject of the sentence: the adoption is the thing that happens / takes place / is carried out.

The article η also shows nominative feminine singular here.

Because γίνεται comes from γίνομαι, which means things like:

• to become
• to happen
• to take place
• to be done / occur

So this sentence is describing an event happening, not simply stating what something is.

• είναι = is
• γίνεται = happens / takes place / is carried out

That is why γίνεται is the natural verb here.

It looks passive to English speakers, but it is better to think of it as a form of the verb γίνομαι, which is a very common Greek verb with middle/passive-style endings.

In this sentence, γίνεται means something like:

• is happening
• takes place
• is being carried out

So yes, in English it may feel passive, but grammatically in Greek it is simply the normal present-tense form of γίνομαι for he/she/it.

It is present tense, third person singular.

So literally it is happens / is happening / takes place.

In Greek, the present can also be used for events that are scheduled for today, so depending on context it may sound like:

• is happening today
• takes place today
• is being finalized today

Because the subject, η υιοθεσία, is singular.

Greek verbs agree with their subject in person and number.

• singular subject → singular verb
• plural subject → plural verb

So:

• Η υιοθεσία γίνεται σήμερα. = singular
• Οι υιοθεσίες γίνονται σήμερα. = plural

Because that is a very normal word order in Greek. Time expressions like σήμερα often come at the end, but Greek word order is fairly flexible.

All of these are possible, though they may shift emphasis slightly:

• Η υιοθεσία γίνεται σήμερα.
• Σήμερα γίνεται η υιοθεσία.
• Η υιοθεσία σήμερα γίνεται. (less neutral, more marked)

The version with σήμερα at the end is a neutral, natural way to say it.

Yes. That means the adoption will take place today.

The difference is:

• γίνεται σήμερα = present tense; can mean is happening today or is taking place today
• θα γίνει σήμερα = future; more clearly will happen today

If the event is still upcoming, θα γίνει σήμερα may be more precise.
If the event is underway, scheduled, or being spoken of as today’s event, γίνεται σήμερα is very natural.

A practical pronunciation guide is:

• Η = ee
• υιοθεσία = yee-o-the-SEE-a
• γίνεται = YEE-ne-te
• σήμερα = SEE-me-ra

A more careful approximation:

• Η υιοθεσία γίνεται σήμερα
• ee yee-o-the-SEE-a YEE-ne-te SEE-me-ra

A couple of useful notes:

• θ sounds like th in think
• γ before ι / ε is pronounced like a soft y-type sound

The stress falls on:

• υιοθεσία
• γίνεται
• σήμερα

Not always. Υιοθεσία can mean:

• adoption in the family/legal sense
• more generally, adoption of an idea, policy, method, system, etc.

So the sentence could refer to a legal adoption, but in another context it could also mean something more abstract, like the adoption of a measure or practice.

Context tells you which meaning is intended.

Usually not in a neutral sentence like this.

• Η υιοθεσία γίνεται σήμερα. = natural
• Υιοθεσία γίνεται σήμερα. = possible only in a special context, but not the normal default

Greek generally prefers the article with nouns when referring to a specific event or concept already known in context.

Because Greek often leaves out information that is either:

• already understood from context
• unknown
• not important to the speaker’s point

Here the focus is on the event itself: the adoption is taking place today.
If you wanted to mention the people involved, Greek could add that information separately, but it is not necessary for the sentence to be complete.

It sounds fairly neutral and somewhat formal, mostly because υιοθεσία is a formal noun and the topic itself is often legal or official.

You might hear this kind of sentence in:

• official announcements
• legal or administrative contexts
• news reports
• formal conversation

It is perfectly natural Greek, just not especially casual in tone because of the subject matter.