Αν ο αρραβωνιαστικός και η αρραβωνιαστικιά αλλάξουν ημερομηνία, θα πρέπει να τυπώσουν ξανά κάθε προσκλητήριο.

Yes, Αν here means if and introduces a condition:

• Αν ... = If ...

In this sentence:

• Αν ο αρραβωνιαστικός και η αρραβωνιαστικιά αλλάξουν ημερομηνία
  = If the fiancé and the fiancée change the date

In Modern Greek, αν is the normal word for real or possible conditions.

This is one of the most common things learners notice.

After αν, Greek often uses the subjunctive-form verb (without να) when talking about a future possibility. That is what αλλάξουν is here.

• αλλάξουν = aorist subjunctive form of αλλάζω
• after αν, this gives the sense if they change

So:

• Αν ... αλλάξουν ... = If they change ...

Greek does not usually match English word-for-word here. English uses a present form (if they change), but Greek often uses this aorist subjunctive form.

By contrast:

• αλλάζουν = they change / they are changing (present indicative)

That would not fit this future conditional sentence naturally.

Because after αν, Greek normally does not use να, even though the verb form is the same kind of form you often see after να.

Compare:

• να αλλάξουν = to change / that they change
• αν αλλάξουν = if they change

So the important thing is:

• after να → subjunctive
• after αν → also this kind of subjunctive-form verb, but without να

This is very normal Greek grammar.

They mean:

• ο αρραβωνιαστικός = the fiancé / the engaged man
• η αρραβωνιαστικιά = the fiancée / the engaged woman

These are the masculine and feminine forms of the same idea.

A learner should also know that in everyday Greek, these words can sometimes feel a little broader in use depending on context, but in a sentence about invitations and changing the date, they very clearly mean an engaged couple.

Because Greek articles must match the gender and number of the noun.

Here:

• ο αρραβωνιαστικός → masculine singular
• η αρραβωνιαστικιά → feminine singular

So Greek says:

• ο for a masculine noun
• η for a feminine noun

This is just standard agreement.

Because the subject is two people joined by και:

• ο αρραβωνιαστικός και η αρραβωνιαστικιά
  = the fiancé and the fiancée

That makes a plural subject, so the verbs are plural:

• αλλάξουν = they change
• τυπώσουν = they print

Even though each noun is singular, together they mean they.

Here θα πρέπει να means will have to or will need to.

Breakdown:

• θα = future marker
• πρέπει = it is necessary / one must
• να τυπώσουν = to print

So:

• θα πρέπει να τυπώσουν
  = they will have to print

A useful nuance:

• πρέπει να by itself often means must / have to
• θα πρέπει να can sometimes mean should in some contexts, but here the meaning is clearly stronger: if they change the date, reprinting the invitations becomes necessary.

So in this sentence, will have to is the best understanding.

Because Greek is choosing the aorist form to present the action as a single whole event:

• να τυπώσουν = to print / to reprint as one completed action
• να τυπώνουν would suggest an ongoing, repeated, or habitual process

In this context, the idea is:

• they will need to print the invitations again, as a one-time task

So τυπώσουν is the natural choice.

This is a very common Greek pattern:

• aorist subjunctive = one complete action
• present subjunctive = ongoing or repeated action

ξανά means again.

So:

• να τυπώσουν ξανά = to print again / to reprint

Its position is very natural in Greek. It often comes after the verb:

• τυπώσουν ξανά

You may also see ξανά in slightly different positions in other sentences, but here this is the most straightforward placement.

Because κάθε means each or every, and in Greek it is followed by a singular noun.

So:

• κάθε προσκλητήριο = each invitation / every invitation

This is similar to English, where we also say:

• every invitation
• not every invitations

So the singular is exactly what you should expect after κάθε.

Here προσκλητήριο means invitation, specifically a printed invitation card.

In the context of an engaged couple and changing the date, it strongly suggests:

• wedding invitation(s)

So:

• κάθε προσκλητήριο = every invitation card

This word can appear in formal contexts, especially for events.

Greek often allows a noun without an article where English might naturally think of the.

So:

• αλλάξουν ημερομηνία literally looks like change date
• but in natural English we would usually say change the date

This kind of article omission can happen especially with common objects or set expressions. Greek does not always require the definite article in places where English does.

If someone said αλλάξουν την ημερομηνία, that could also be possible in many contexts, but the article-less version is very natural here.

The subject nouns are in the nominative:

• ο αρραβωνιαστικός
• η αρραβωνιαστικιά

because they are the ones doing the actions.

The objects are in the accusative:

• ημερομηνία
• κάθε προσκλητήριο

A small detail that can confuse learners: some noun forms look the same in nominative and accusative, especially neuter nouns and many feminine nouns.

For example:

• προσκλητήριο is neuter, and nominative/accusative singular look the same
• ημερομηνία also has the same form in nominative and accusative singular, though the article would differ if there were one

So the role in the sentence tells you the case, not always the ending alone.

Because once the subject has already been clearly stated, Greek often leaves it out with later verbs if it is the same subject.

So Greek says:

• Αν ο αρραβωνιαστικός και η αρραβωνιαστικιά αλλάξουν ημερομηνία, θα πρέπει να τυπώσουν ξανά κάθε προσκλητήριο.

It does not need to repeat:

• ... θα πρέπει αυτοί να τυπώσουν ...

That repetition would usually be unnecessary unless you wanted special emphasis.

This is very common in Greek, since the verb ending already helps show who the subject is.

Yes.

They come from the same root:

• αρραβώνας = engagement
• αρραβωνιαστικός = fiancé
• αρραβωνιαστικιά = fiancée

This is useful vocabulary-building: once you know one word in the family, the others become easier to recognize.

Yes, absolutely.

That is a very natural English translation. Greek spells out the two people individually:

• ο αρραβωνιαστικός και η αρραβωνιαστικιά

but English can naturally compress that to:

• the engaged couple
• the fiancé and fiancée

Also, τυπώσουν ξανά can very naturally be translated as:

• print again
• reprint

So reprint every invitation is a very good natural rendering.

It has a very common Greek pattern:

• Αν + verb = condition
• θα + verb/expression = result

So the structure is:

• Αν
  • they change the date,
• θα πρέπει να
  • they print every invitation again

In simple terms:

1. condition: if they change the date
2. consequence: they will have to reprint every invitation

This is one of the most useful sentence patterns in everyday Greek.