Learn Hardcore Greek: Στο σεμινάριο η εθελόντρια εξηγεί το πρόγραμμα. - At the seminar the volunteer female explains the schedule.

The preposition σε is followed by the accusative case.
The noun is το σεμινάριο (the seminar).
- Nominative: το σεμινάριο (subject form)
- Accusative: το σεμινάριο (object / after preposition)

For many neuter nouns ending in -ο, the nominative and accusative forms are identical. So it happens to look the same; the function (here: after a preposition) tells you it’s accusative.

Why do we say στο σεμινάριο (with “the”) instead of just σε σεμινάριο?

Greek uses the definite article much more often than English.

στο σεμινάριο = at the seminar (a specific seminar that speaker and listener know about)
σε σεμινάριο or σε ένα σεμινάριο = at a seminar (some seminar, not specific)

In everyday Greek, when you have a concrete place or event that is known or identifiable from context, you almost always use the article:

στο σχολείο = at school
στη δουλειά = at work
στο σεμινάριο = at the seminar

What is η εθελόντρια exactly in terms of gender and form?

η εθελόντρια means the (female) volunteer.

εθελοντής = volunteer (masculine)
εθελόντρια = volunteer (feminine)

Form details:

η = the (feminine singular, nominative)
εθελόντρια = noun, feminine, nominative singular

It is the subject of the sentence: η εθελόντρια εξηγεί… = the volunteer explains…

Why is there an article (η) before εθελόντρια? Could we drop it?

In Greek, you normally use the definite article with singular countable nouns when you are talking about a specific person or thing.

η εθελόντρια = the (specific) volunteer
Saying just εθελόντρια εξηγεί το πρόγραμμα is possible but sounds either:
- like a headline / very “telegram-style”, or
- very unusual in normal speech.

You would drop the article only in special cases (titles, headlines, vocative, etc.). In a normal sentence, η εθελόντρια is the natural form.

Why is there no subject pronoun like αυτή (“she”) before εξηγεί?

Greek is a “pro‑drop” language: subject pronouns are usually omitted because the verb ending shows who the subject is.

εξηγεί = he explains / she explains / it explains

Here, η εθελόντρια is the subject. Adding αυτή would be:

Στο σεμινάριο αυτή η εθελόντρια εξηγεί το πρόγραμμα.

This is possible, but it changes the emphasis to this volunteer (not another one) and sounds more contrastive. In neutral sentences, you don’t use αυτός/αυτή/αυτό unless you want emphasis or contrast.

What tense and person is εξηγεί, and what does it correspond to in English?

εξηγεί is:

Verb: εξηγώ = to explain
Tense: Present
Person: 3rd person singular (he / she / it)
Form: (αυτός/αυτή/αυτό) εξηγεί

Greek present tense usually covers both:

English simple present: she explains the program (in general)
English present continuous: she is explaining the program (right now)

The exact meaning depends on context. On its own, εξηγεί can mean either.

What is the role and form of το πρόγραμμα in the sentence?

το πρόγραμμα means the program and is the direct object of the verb εξηγεί.

Form details:

το = the (neuter singular, nominative/accusative)
πρόγραμμα = neuter noun, singular, accusative here

It is in the accusative case because:

Direct objects of verbs take the accusative in Greek.

Using the article το again shows we are talking about some specific program, known from context (e.g. the schedule of the seminar).

Could we change the word order, for example: Η εθελόντρια στο σεμινάριο εξηγεί το πρόγραμμα? Does the meaning change?

Yes, Greek word order is flexible. These versions are all grammatical:

Στο σεμινάριο η εθελόντρια εξηγεί το πρόγραμμα.
– At the seminar, the volunteer explains the program.
(Initial phrase Στο σεμινάριο sets the scene / location.)
Η εθελόντρια στο σεμινάριο εξηγεί το πρόγραμμα.
– The volunteer, at the seminar, explains the program.
(More focus on η εθελόντρια, with στο σεμινάριο as an extra detail.)
Η εθελόντρια εξηγεί το πρόγραμμα στο σεμινάριο.
– The volunteer explains the program at the seminar.
(Neutral English-like order: subject–verb–object–place.)

The core meaning is the same; differences are nuance and emphasis.

What is the difference between σε and forms like στο, στη, στον?

σε is the basic preposition: in / at / to.

When it is followed by a definite article, they usually merge:

σε + το = στο (neuter or masculine accusative)
- στο σεμινάριο – at the seminar
σε + τον = στον (masculine accusative)
- στον καθηγητή – to the (male) teacher
σε + την = στην (feminine accusative)
- στην πόλη – in the city

So στο in the sentence is σε + το.

How is the whole sentence pronounced, and where are the stress accents?

Sentence: Στο σεμινάριο η εθελόντρια εξηγεί το πρόγραμμα.

Stressed syllables (marked with capitals here):

sto se-mi-NÁ-ri-o i e-the-LÓN-tri-a e-ksi-GÍ to PRÓ-gram-ma

Approximate phonetic transcription (IPA):

/sto semiˈnario i eθeˈlondria eksiˈʝi to ˈproɣrama/

Stress in Greek is always marked with an accent on one syllable in each word with more than one syllable:
σεμινάριο, εθελόντρια, εξηγεί, πρόγραμμα.

How would the sentence change if there were several female volunteers instead of one?

You would make the subject and verb plural:

Singular:
- Η εθελόντρια εξηγεί το πρόγραμμα.
  = The (female) volunteer explains the program.
Plural:
- Οι εθελόντριες εξηγούν το πρόγραμμα.
  = The (female) volunteers explain the program.

Full sentence in the plural:

Στο σεμινάριο οι εθελόντριες εξηγούν το πρόγραμμα.
– At the seminar, the (female) volunteers explain the program.