Learn Hardcore Greek: Αύριο θα παραδώσουν όλα τα πακέτα πριν το μεσημέρι, σύμφωνα με την υπενθύμιση που πήρα στο κινητό. - Tomorrow they will deliver all the packages before noon, according to the reminder I got on my phone.

θα παραδώσουν is 3rd person plural (they will deliver).
The -ουν ending tells us the subject is they, so αυτοί is not needed.
You would only add αυτοί for emphasis or contrast, e.g.
Αύριο αυτοί θα παραδώσουν όλα τα πακέτα. = Tomorrow *they (as opposed to others) will deliver all the packages.*

What exactly is the tense/aspect of θα παραδώσουν, and why not παραδίδουν?

Θα παραδώσουν is the simple future (perfective aspect):

Verb: παραδίδω (I deliver, I hand over – present, imperfective)
Simple future (perfective): θα παραδώσω, θα παραδώσεις, …, θα παραδώσουν

Use:

θα παραδώσουν = they will deliver (once / as a completed whole action)
→ Focus on the fact that the delivering will be completed.
παραδίδουν (present, imperfective) = they deliver / they are delivering / they deliver regularly
→ Used for habits or ongoing situations, not for a specific future one-off event like here.

So Αύριο θα παραδώσουν fits because it’s about one future completed task tomorrow.

Why is the object όλα τα πακέτα placed after the verb (θα παραδώσουν όλα τα πακέτα) instead of before it?

Greek word order is flexible. Both are possible:

Αύριο θα παραδώσουν όλα τα πακέτα…
Αύριο όλα τα πακέτα θα παραδώσουν…

Default, neutral order tends to be:

[Time] – [Verb] – [Object] – [Other information]

Putting όλα τα πακέτα after the verb sounds natural and neutral here.
If you move όλα τα πακέτα in front of the verb, you slightly emphasize όλα τα πακέτα (all of the packages):

Αύριο όλα τα πακέτα θα παραδώσουν…
→ Emphasis: all the packages, not just some.

In everyday speech, the sentence as given is the most typical version.

Why do we say πριν το μεσημέρι and not just πριν μεσημέρι?

In Greek, times of day usually take the definite article:

το πρωί, το μεσημέρι, το απόγευμα, το βράδυ etc.

With πριν followed by a noun, you normally keep the article:

πριν το μεσημέρι = before noon
πριν το βράδυ = before the evening

πριν μεσημέρι sounds ungrammatical or at least very odd in standard Greek.

You can also hear:

πριν από το μεσημέρι – adding από.
πριν το μεσημέρι and πριν από το μεσημέρι are both correct; πριν το μεσημέρι is just a little shorter and very common.

What is the difference between πριν το μεσημέρι and μέχρι το μεσημέρι?

Both relate to time limits but the nuance is different:

πριν το μεσημέρι
= at some point before noon
It just says the action will be completed earlier than noon.
μέχρι το μεσημέρι
= by noon / up until noon
It suggests a time limit or deadline that lasts up to noon.

In this sentence, πριν το μεσημέρι works well because it’s simply stating the deliveries will be completed sometime before noon, not necessarily right at the deadline.

What does σύμφωνα με mean exactly, and why do we need με here?

σύμφωνα με is a fixed expression meaning according to.

σύμφωνα by itself is an adverb meaning in agreement, in accordance.
Combined with με
- accusative, it makes the prepositional phrase:
  - σύμφωνα με την υπενθύμιση = according to the reminder
  - σύμφωνα με τον νόμο = according to the law
  - σύμφωνα με τα στοιχεία = according to the data

You cannot replace με with another preposition here; σύμφωνα με behaves as a single unit.

Why is it σύμφωνα με την υπενθύμιση and not υπενθύμισης or some other case?

In modern Greek, most prepositions (including με) take the accusative case.

Noun: η υπενθύμιση (reminder – nominative)
Accusative singular: την υπενθύμιση

So:

σύμφωνα με + [accusative]
→ σύμφωνα με την υπενθύμιση, σύμφωνα με τον κανόνα, σύμφωνα με τα στοιχεία.

A genitive form like υπενθύμισης would be wrong here because the preposition με does not govern the genitive.

How does the relative clause που πήρα στο κινητό work? Can που here mean both that and which?

Yes. In modern Greek, που is the standard, invariable relative pronoun for who/that/which in most everyday contexts.

την υπενθύμιση που πήρα στο κινητό
= the reminder (that/which) I received on my phone

Points to note:

που does not change form for gender, number, or case.
It is used for people, things, and abstract nouns.
More formal alternatives exist (η οποία, το οποίο etc.), e.g.
σύμφωνα με την υπενθύμιση, την οποία πήρα στο κινητό (μου)
but that sounds more formal or written.

So English that and which in this context are both covered by Greek που.

Why is the past tense πήρα used in που πήρα στο κινητό, and not something like έπαιρνα?

Πήρα is the aorist (simple past) of παίρνω:

παίρνω = I take / I get / I receive (imperfective)
πήρα = I took / I got / I received (aorist, perfective – single, completed event)

Here, receiving the reminder is:

One completed event in the past → πήρα is the natural choice.

Έπαιρνα (imperfect past) would describe a repeated or ongoing past action, like:

Κάθε μέρα έπαιρνα υπενθυμίσεις στο κινητό.
= Every day I was getting / used to get reminders on my phone.

In our sentence, it refers to one specific reminder that you got, so πήρα is correct.

Why is it στο κινητό and not στο κινητό μου when in English we say on my phone?

στο κινητό is short for σε + το κινητό = on the mobile (phone).

Greek often omits possessive pronouns (μου, σου, etc.) when it’s obvious who owns the object, especially for:

Body parts: έπλυνα τα χέρια (I washed my hands)
Personal items: πήρα το κινητό (I took my phone)

In this context, στο κινητό almost always implies your own phone, so adding μου is optional:

στο κινητό = on my phone (understood from context)
στο κινητό μου = on my phone (explicit)

Both are correct; στο κινητό just sounds slightly more casual and typical.

What exactly does κινητό mean here, and why is there no word for phone after it?

κινητό is a shortened form of κινητό τηλέφωνο (mobile phone / cell phone).

In everyday Greek:

το κινητό by itself almost always means mobile phone.
People rarely say the full κινητό τηλέφωνο in casual speech unless they want to be very clear or formal.

Grammatically:

κινητό is a neuter adjective meaning mobile / movable used as a noun.
With article: το κινητό = the mobile (phone).

So στο κινητό is perfectly natural: on the mobile (phone).

Could we also say Αύριο θα παραδοθούν όλα τα πακέτα πριν το μεσημέρι? What’s the difference?

Yes, that’s also correct but it changes from active to passive voice.

θα παραδώσουν όλα τα πακέτα
= Active: They will deliver all the packages.
- Implied subject: they (courier company, postal service, etc.).
θα παραδοθούν όλα τα πακέτα
= Passive: All the packages will be delivered.
- Focus is on the packages; the deliverer is not mentioned.

Both are grammatical. The original sentence emphasizes the agents (they will deliver), even though they’re not named. The passive version emphasizes the result (the packages will be delivered).

Can Αύριο be moved elsewhere in the sentence? Is its position fixed?

Αύριο is flexible. All of these are possible and natural:

Αύριο θα παραδώσουν όλα τα πακέτα πριν το μεσημέρι…
Θα παραδώσουν αύριο όλα τα πακέτα πριν το μεσημέρι…
Θα παραδώσουν όλα τα πακέτα αύριο πριν το μεσημέρι…
(a little redundant with πριν το μεσημέρι, but still grammatical)

General rule:

Time adverbs like αύριο, σήμερα, μετά can appear at the beginning, after the verb, or even at the end, with only slight changes in emphasis or rhythm.
Starting with Αύριο is a very common, neutral way to frame a future event.