Learn Hardcore Greek: Όσοι θέλουν να βοηθήσουν μπορούν να συμμετέχουν σε ένα σεμινάριο το Σάββατο. - Whoever wants to help can participate in a seminar on Saturday.

Όσοι literally means those (people) who / everyone who.
The full, more “neutral” version would be Αυτοί που θέλουν να βοηθήσουν = those who want to help.

Differences in nuance:

Όσοι is shorter and a bit more formal or “written”, commonly used in announcements, instructions, etc.
Αυτοί που is more everyday and very common in spoken language.

In most contexts, Όσοι θέλουν να βοηθήσουν ≈ Αυτοί που θέλουν να βοηθήσουν, with almost the same meaning.

Why is Όσοι masculine plural? What if we’re talking only about women?

Όσοι is the masculine nominative plural form of the relative pronoun that means those who.
In Greek, as in many languages, the masculine plural is the default when talking about:

a mixed group (men + women), or
people in general, when gender is unknown or irrelevant.

If you are talking about only women, you would say:

Όσες θέλουν να βοηθήσουν… = “(All) the women who want to help…”

There is also Όσα (neuter plural) for things or sometimes for children/animals, depending on context.

Why is the verb θέλουν plural? What is the subject of the sentence?

The subject is Όσοι (“those who / everyone who”).
Since Όσοι is plural, the verb must also be plural:

Όσοι (they) θέλουν (they want)

So:

Όσοι θέλουν = “Those who want” → subject and verb agree in number (plural) and person (3rd person).

The same applies to μπορούν:

Όσοι … μπορούν = “Those who … can”.

What exactly does θέλουν να βοηθήσουν mean, and why is it βοηθήσουν and not βοηθάνε?

Θέλουν να βοηθήσουν literally: they want to help.

θέλουν = “they want” (present indicative)
να βοηθήσουν = “to help” (aorist subjunctive of βοηθάω/βοηθώ)

Greek uses two aspects in the subjunctive:

να βοηθήσουν (aorist aspect) → focuses on the whole action of helping, usually as a single event.
να βοηθάνε (present aspect) → would focus on ongoing/repeated helping.

Here, the idea is “those who want to help (in this specific thing/situation)”, so the aorist να βοηθήσουν is more natural.

What is the role of να in να βοηθήσουν and να συμμετέχουν? Is it like “to” in English?

Να is mainly a subjunctive marker in Modern Greek. It does not exactly equal English “to”, although it often appears where English uses “to + verb”.

In να βοηθήσουν, να συμμετέχουν:

να shows that the following verb is in the subjunctive mood, often after verbs like θέλω (I want), μπορώ (I can), πρέπει (I must), etc.
It can introduce wishes, possibilities, obligations, purposes, etc.

So grammatically, να is not an infinitive marker (Greek has no true infinitive); it signals a subjunctive clause.

Why is it να βοηθήσουν (aorist) but να συμμετέχουν (present)? Is there a difference in meaning?

Yes, this is a good example of aspect in Greek:

να βοηθήσουν (aorist subjunctive) – one complete action of helping, seen as a whole event.
→ “those who want to (come and) help (in this specific action)”
να συμμετέχουν (present subjunctive) – ongoing or repeated participation.
→ “can be participating / can take part (in general or during that period)”

In this sentence, the combination suggests:

They want to help (one concrete cause/action),
and they can be participating in a seminar (an activity that lasts some time during Saturday).

Aorist vs present subjunctive often gives this nuance: single/whole event vs ongoing/repeated action.

What does μπορούν να συμμετέχουν literally mean, and why do we need μπορούν?

Μπορούν να συμμετέχουν = they can participate, they are able to take part.

μπορούν = “they are able to / they can”
να συμμετέχουν = “to participate” (present subjunctive)

Without μπορούν,

συμμετέχουν σε ένα σεμινάριο would mean “they participate in a seminar” (statement of fact).
With μπορούν,
it expresses possibility/permission: “they have the option/ability to participate”.

So μπορούν is necessary to give the meaning can / are allowed / are able.

What does συμμετέχω mean compared to something like παίρνω μέρος?

Συμμετέχω and παίρνω μέρος are very close in meaning: to participate / to take part.

συμμετέχω σε ένα σεμινάριο
παίρνω μέρος σε ένα σεμινάριο

Both are correct.
Differences:

συμμετέχω is a single verb, a bit more formal/standard, common in written texts, announcements, etc.
παίρνω μέρος is a verb phrase, very common in speech and writing; slightly more colloquial in tone but still standard.

In your sentence, you could also say:

…μπορούν να πάρουν μέρος σε ένα σεμινάριο το Σάββατο.

Why do we say συμμετέχω σε ένα σεμινάριο and not with some other preposition?

Συμμετέχω is typically followed by σε:

συμμετέχω σε κάτι = “I participate in something / I take part in something”.

So:

συμμετέχουν σε ένα σεμινάριο = “they participate in a seminar”.

This is just how the verb συμμετέχω is constructed in Greek:

συμμετέχω σε
- noun.

Why is it σε ένα σεμινάριο and not στο σεμινάριο? What difference does the article make?

Ένα is the indefinite article (“a/an”), while το is the definite article (“the”).

σε ένα σεμινάριο = in a seminar / at a seminar (unspecified, any such seminar)
στο σεμινάριο (σε + το) = in the seminar (a specific seminar already known from context)

Here, the sentence introduces the idea of “a seminar on Saturday” for the first time, not a particular one already known, so σε ένα σεμινάριο (“to a seminar”) is more natural.

Why do we say το Σάββατο and not just Σάββατο? Is there a difference?

Both forms exist, but they’re used a bit differently:

το Σάββατο = “on Saturday” (referring to a specific upcoming Saturday, usually the next one)
- Θα πάω στο σεμινάριο το Σάββατο. → “I’ll go to the seminar on Saturday (this coming Saturday).”
Σάββατο without the article can be used more like a label or in very short phrases, but for “on Saturday” it’s very common and natural to include the article το.

In everyday speech, την Κυριακή, τη Δευτέρα, το Σάββατο etc. with the article is the default for “on [day]” when referring to a particular occurrence.

Can the word order change? For example, can we say Όσοι θέλουν να βοηθήσουν μπορούν το Σάββατο να συμμετέχουν σε ένα σεμινάριο?

Yes, Greek word order is relatively flexible, and your example is grammatically correct:

Όσοι θέλουν να βοηθήσουν μπορούν το Σάββατο να συμμετέχουν σε ένα σεμινάριο.

Main points:

The core structure Όσοι … μπορούν να συμμετέχουν σε ένα σεμινάριο must stay intact.
Time expressions like το Σάββατο can move around (beginning, middle, end) without changing the basic meaning, only the emphasis.

For example:

Το Σάββατο όσοι θέλουν να βοηθήσουν μπορούν να συμμετέχουν σε ένα σεμινάριο.
emphasises Saturday more.

Could we say Όσοι θέλουν να βοηθήσουν συμμετέχουν σε ένα σεμινάριο το Σάββατο without μπορούν?

Yes, but the meaning changes.

Όσοι θέλουν να βοηθήσουν μπορούν να συμμετέχουν…
→ “Those who want to help can participate…” (it’s an offer/possibility).
Όσοι θέλουν να βοηθήσουν συμμετέχουν σε ένα σεμινάριο…
→ “Those who want to help participate in a seminar…” (it states what they actually do, as a fact or rule).

So μπορούν adds the idea of permission/possibility/option, not just a description of reality.

In θέλουν να βοηθήσουν, could we also use θέλουν να βοηθάνε? When would that be appropriate?

Θέλουν να βοηθάνε is grammatically possible, but the nuance is different:

Θέλουν να βοηθήσουν → they want to help (in this specific situation / once).
Θέλουν να βοηθάνε → they want to be helping (continuously / regularly), e.g. they want to be generally helpful, or help on an ongoing basis.

In your sentence, which talks about a concrete offer (a seminar on Saturday), the aorist να βοηθήσουν is the natural choice. Να βοηθάνε would sound more like a general habit or continuous attitude.

Is there an implied subject pronoun like αυτοί in this sentence, or is Όσοι enough?

Όσοι itself functions as the subject; there is no need (and it would be wrong) to add αυτοί here.

Όσοι θέλουν να βοηθήσουν μπορούν…
→ Όσοι is the subject of both θέλουν and μπορούν.

Greek often omits subject pronouns (like αυτός, αυτοί) because verb endings and words like Όσοι already show who the subject is.

In speech, would σε ένα σεμινάριο sound different? Do people contract σε ένα?

Yes, in natural spoken Greek, σε ένα is very often pronounced as σ’ ένα:

Written (more careful): σε ένα σεμινάριο
Spoken / also written in dialogues: σ’ ένα σεμινάριο

The meaning is the same; it’s just a phonetic contraction that makes speech smoother. You will hear this kind of contraction very often with σε + words starting with a vowel.