Learn Hardcore Greek: Αν ισχύει ο νέος κανόνας, θα χρειαστεί και υπογραφή στο τέλος. - If the new rule applies, a signature will be needed at the end too.

Αν introduces a conditional clause (if...).
In Αν ισχύει ο νέος κανόνας, the verb ισχύει is in the present tense, so the condition is phrased as “if the new rule is valid / is in force (at the relevant time).”
This is a very common pattern: Αν + present (condition) → θα + verb (result).

Could it be εάν instead of αν?

Yes. εάν is a slightly more formal/explicit variant of αν. In everyday writing and speech, αν is extremely common. The meaning is the same in this sentence.

Why is there a comma after κανόνας?

Greek typically uses a comma to separate an introductory conditional clause from the main clause, especially when the Αν... clause comes first:

Αν ισχύει ο νέος κανόνας, (condition)
θα χρειαστεί... (result)

The comma is standard and helps readability.

What does ισχύει mean, and why not use a verb like είναι?

ισχύω means to be valid, to apply, to be in force (often for rules, laws, regulations, agreements, statements). So Αν ισχύει ο νέος κανόνας is more precise than Αν είναι ο νέος κανόνας..., which would not sound right because είμαι just means to be, not to be legally/officially in effect.

Is ο νέος κανόνας the subject of ισχύει? Why is it in this form?

Yes. ο νέος κανόνας (the new rule) is the subject of ισχύει, so it’s in the nominative case:

ο κανόνας = nominative singular masculine (the rule)
νέος agrees with κανόνας (masculine, singular, nominative)

Why does the main clause use θα χρειαστεί?

θα marks the future (or future-like prediction).
χρειαστεί is the form used here to mean it will be needed / it will be necessary.

So the structure is:

θα + χρειαστεί = will be needed / will be required

Is θα χρειαστεί passive? Who is doing the needing?

It’s not passive in the “by someone” sense; it’s a very common impersonal/neutral way to express requirement in Greek:

Χρειάζεται υπογραφή. = A signature is needed.
Θα χρειαστεί υπογραφή. = A signature will be needed.

Greek often avoids naming an agent when stating requirements.

Why is it υπογραφή without μια or η?

Greek often omits the article when talking about a requirement in a general/indefinite way, similar to English “Signature required”:

θα χρειαστεί υπογραφή ≈ a signature will be needed / signature will be required

You can add something if you want to specify:

θα χρειαστεί μια υπογραφή = one/a signature will be needed (more specific)
θα χρειαστεί η υπογραφή = the signature will be needed (a particular known signature)

What does και mean here, and why is it placed before υπογραφή?

Here και means also / as well:
θα χρειαστεί και υπογραφή = a signature will also be needed.

Placing και right before υπογραφή emphasizes that the extra item is the signature (in addition to something else already expected).

What does στο τέλος mean, and how is στο formed?

στο τέλος means at the end.
στο is a contraction of:

σε (in/at/to) + το (the, neuter singular) → στο

And τέλος is neuter, so it takes το:

το τέλος = the end
στο τέλος = at the end

Could the sentence use Αν ισχύσει instead of Αν ισχύει?

Yes, and it slightly changes the nuance:

Αν ισχύει = if it is valid / if it applies (treated as a current/general condition)
Αν ισχύσει = if it becomes valid / if it ends up applying (more “if it turns out to be in force”)

Both can be correct depending on context; Αν ισχύει is very natural when you’re talking about a rule that may currently apply.

Why doesn’t Greek use something like will need with a person as subject (e.g., “we will need”)?

Greek can do that, but it changes the focus. This sentence is framed as a requirement, not someone’s need:

Θα χρειαστούμε υπογραφή. = We will need a signature. (focus on “we”)
Θα χρειαστεί υπογραφή. = A signature will be needed. (focus on the requirement)

The original is more “official/procedural” in tone.

Is the word order flexible? Could I move parts around?

Yes, Greek word order is fairly flexible, but changes can affect emphasis. For example:

Θα χρειαστεί και υπογραφή στο τέλος. (result first; still natural)
Στο τέλος θα χρειαστεί και υπογραφή. (emphasizes at the end)
Και υπογραφή θα χρειαστεί στο τέλος. (strong emphasis on signature as an added requirement)

The given version is a neutral, very standard layout.