Τα πιάτα θα πλυθούν και το πάτωμα θα καθαριστεί όταν τελειώσει το σεμινάριο.

The dishes will be washed and the floor will be cleaned when the seminar finishes.

Breakdown of Τα πιάτα θα πλυθούν και το πάτωμα θα καθαριστεί όταν τελειώσει το σεμινάριο.

• και: and
• θα: will
• όταν: when
• το πιάτο: the plate
• τελειώνω: to finish
• καθαρίζομαι: to be cleaned
• το πάτωμα: the floor
• το σεμινάριο: the seminar
• πλένομαι: to be washed

Questions & Answers about Τα πιάτα θα πλυθούν και το πάτωμα θα καθαριστεί όταν τελειώσει το σεμινάριο.

Why is the passive voice used here (θα πλυθούν, θα καθαριστεί) instead of the active?

The sentence focuses on the result (clean dishes, clean floor) rather than on who is doing the action.

• Τα πιάτα θα πλυθούν = The dishes will be washed (we don’t care / don’t say who will wash them).
• το πάτωμα θα καθαριστεί = the floor will be cleaned (again, the doer is not mentioned).

In Greek, as in English, the passive is often used when:

• the agent is obvious (e.g. the people who took the seminar),
• unimportant,
• or deliberately not mentioned.

An active version would be:
Κάποιος θα πλύνει τα πιάτα και θα καθαρίσει το πάτωμα όταν τελειώσει το σεμινάριο.
(Someone will wash the dishes and clean the floor when the seminar is over.)

The meaning is similar, but the focus shifts from the dishes/floor to the person doing the actions.

How is θα πλυθούν formed from the verb πλένω?

Πλένω = I wash (active).
Greek has an active and a (middle-)passive set of forms.

For πλένω:

• Present active: πλένω – I wash
• Aorist (simple past) passive: πλύθηκα – I was washed
• Future passive: θα πλυθώ – I will be washed

To get θα πλυθούν:

1. Take the passive stem: πλυθ- (from πλύθηκα).
2. Add the future marker θα
   • passive endings.
     
     • 1st sing.: θα πλυθώ
     • 2nd sing.: θα πλυθείς
     • 3rd sing.: θα πλυθεί
     • 1st pl.: θα πλυθούμε
     • 2nd pl.: θα πλυθείτε
     • 3rd pl.: θα πλυθούν

So θα πλυθούν is the 3rd person plural future passive, matching the plural noun τα πιάτα (the dishes).

How is θα καθαριστεί formed from καθαρίζω?

Καθαρίζω = I clean (active).

Key forms:

• Present active: καθαρίζω – I clean
• Present passive: καθαρίζομαι – I am cleaned / I get cleaned
• Aorist passive: καθαρίστηκα – I was cleaned
• Future passive: θα καθαριστώ – I will be cleaned

To form θα καθαριστεί:

1. Passive stem: καθαρισ- (from καθαρίστηκα, θα καθαριστώ).

2. Future marker θα

   • passive endings:
   • 1st sing.: θα καθαριστώ
   • 2nd sing.: θα καθαριστείς
   • 3rd sing.: θα καθαριστεί
   • 1st pl.: θα καθαριστούμε
   • 2nd pl.: θα καθαριστείτε
   • 3rd pl.: θα καθαριστούν

Θα καθαριστεί is 3rd person singular future passive, agreeing with το πάτωμα (singular neuter).

What is the difference between θα πλυθούν and θα πλύνουν?

They are different voice and different subjects:

• θα πλυθούν

  • Voice: passive
  • Subject: τα πιάτα (the dishes)
  • Meaning: The dishes will be washed.

• θα πλύνουν (from πλένω)

  • Voice: active
  • Subject: some they (implicit)
  • Meaning: They will wash (something).

Examples:

• Τα πιάτα θα πλυθούν.
  The dishes will be washed. (focus on dishes)

• Θα πλύνουν τα πιάτα.
  They will wash the dishes. (focus on the people)

So -θούν is a passive ending, while -ουν (or -ουν(ε)) is a 3rd person plural active ending.

Why do we say όταν τελειώσει το σεμινάριο and not όταν θα τελειώσει το σεμινάριο?

In Modern Greek, when you talk about the future in a clause of time introduced by words like:

• όταν (when),
• μόλις (as soon as),
• αφού (in some uses, after / once),

you normally use the subjunctive without θα, not the future with θα.

So:

• Correct: Όταν τελειώσει το σεμινάριο, …
• Not natural: Όταν θα τελειώσει το σεμινάριο, …

Compare:

• Θα φύγω όταν τελειώσει το σεμινάριο.
  I’ll leave when the seminar is over.

Literally: I will leave when the seminar finish‑SUBJ.
The future meaning is already implied by όταν + subjunctive, so Greek does not add θα inside that time clause.

What exactly is τελειώσει here? Why not τελειώνει?

Τελειώσει is the aorist (perfective) subjunctive, 3rd person singular, from τελειώνω (to finish, to end).

• Present indicative: τελειώνει – it finishes / it is finishing
• Aorist subjunctive: να τελειώσει – to finish (as a single complete event)
• In the sentence, the να is dropped because όταν takes the same subjunctive form:
  όταν τελειώσει = when it finishes / when it is over (at that moment)

Why not όταν τελειώνει?

• όταν τελειώνει το σεμινάριο usually describes something habitual or repeated:
  When the seminar (usually) ends, … (every time).
• όταν τελειώσει το σεμινάριο refers to one specific future completion of the seminar.

In this sentence, we’re talking about one event in the future (this seminar finishing), so the aorist/perfective subjunctive τελειώσει is appropriate.

Can the order of the clauses be changed, for example starting with Όταν τελειώσει το σεμινάριο?

Yes. Greek word order here is flexible. You can say:

• Τα πιάτα θα πλυθούν και το πάτωμα θα καθαριστεί όταν τελειώσει το σεμινάριο.
• Όταν τελειώσει το σεμινάριο, τα πιάτα θα πλυθούν και το πάτωμα θα καθαριστεί.

Both are correct and natural.

Punctuation changes slightly:

• When the όταν‑clause comes first, you usually put a comma after it.
• When it comes after the main clause, typically no comma is used, as in your sentence.

The meaning is the same. Starting with Όταν τελειώσει το σεμινάριο just puts more emphasis on the time condition.

Why do we need the definite articles τα, το, and το? Could we drop them?

In Greek, the definite article is used much more often than “the” in English, and it is usually required with countable nouns in this kind of sentence.

• Τα πιάτα – the dishes
• το πάτωμα – the floor
• το σεμινάριο – the seminar

Here we are referring to specific, identifiable things:

• the dishes from this meal,
• the floor in this room,
• the seminar we are currently talking about.

Because of that, Greek strongly prefers the definite article.
Without the articles:

• Πιάτα θα πλυθούν και πάτωμα θα καθαριστεί όταν τελειώσει σεμινάριο.

This sounds unnatural and even somewhat ungrammatical in modern standard Greek.

So in this context, you should not drop the articles.

Why is there no comma before όταν in this sentence?

In Greek punctuation, the rule of thumb is:

• If the subordinate clause comes first:
  → Use a comma.
  Όταν τελειώσει το σεμινάριο, τα πιάτα θα πλυθούν…

• If the main clause comes first and the time clause is closely attached:
  → Often no comma.
  Τα πιάτα θα πλυθούν και το πάτωμα θα καθαριστεί όταν τελειώσει το σεμινάριο.

You could sometimes see a comma before όταν, but in neutral standard writing, in this exact structure, it is usually omitted. The version you have is perfectly normal punctuation.

How would I say who is going to do the washing and cleaning, if I want to mention the agent?

You can keep the passive and add an agent phrase with από (by), or you can switch to the active voice.

1. Passive with an agent:

• Τα πιάτα θα πλυθούν από τους συμμετέχοντες και το πάτωμα θα καθαριστεί από το προσωπικό όταν τελειώσει το σεμινάριο.
  The dishes will be washed by the participants and the floor will be cleaned by the staff when the seminar is over.

2. Active:

• Οι συμμετέχοντες θα πλύνουν τα πιάτα και το προσωπικό θα καθαρίσει το πάτωμα όταν τελειώσει το σεμινάριο.
  The participants will wash the dishes and the staff will clean the floor when the seminar is over.

Both are grammatical; choosing passive vs active is mainly about what you want to emphasize: the result or the people doing the work.

Could I use the present passive instead of the future, like Τα πιάτα πλένονται?

You can use the present passive, but the meaning changes.

• Τα πιάτα θα πλυθούν όταν τελειώσει το σεμινάριο.
  Future passive: The dishes will be washed when the seminar is over.
  → A future action, not yet happening.

• Τα πιάτα πλένονται όταν τελειώνει το σεμινάριο.
  Present passive + present: The dishes are washed when the seminar ends.
  → Describes a habit / routine: every time a seminar ends, the dishes are washed.

In your original sentence, we’re talking about what will happen after this particular seminar, so the future passive (θα πλυθούν, θα καθαριστεί) is the natural choice.