Learn Hardcore Greek: Αν δεν τη βρεις, θα σου τη στείλω ξανά και θα σου την εξηγήσω αργά. - If you don't find it, I will send it to you again and I will explain it to you slowly.

τη and την are the same pronoun: feminine singular accusative (her / it). The -ν at the end is often dropped in writing before many consonants.

A common spelling rule in Modern Greek:

Keep the -ν (write την) when the next word starts with:
- a vowel: την εξηγήσω
- κ, π, τ, γκ, μπ, ντ, ξ, ψ, or consonant clusters beginning with κ, π, τ
You may drop the -ν (write τη) before other consonants:
- β, δ, γ, ζ, θ, λ, μ, ν, ρ, σ, φ, χ
  → so τη βρεις (because βρεις starts with β)

So:

τη βρεις → next word starts with β, so the ν is dropped
την εξηγήσω → next word starts with a vowel (ε), so we keep ν

In speech, many people pronounce την all the time; the difference is mostly a spelling convention.

What do τη / την refer to in this sentence?

τη / την is the object pronoun “her / it” referring back to a feminine singular noun mentioned earlier in the conversation, for example:

η άσκηση (the exercise)
η λέξη (the word)
η εξήγηση (the explanation)

Greek pronouns must agree in gender and number with the noun:

feminine singular noun → την / τη
masculine singular noun → τον / το
neuter singular noun → το

So here τη / την = “it” (that specific feminine thing you are supposed to find, resend, and explain).

Why do we have both σου and τη before στείλω? What is their order?

Greek allows you to put both the indirect and direct object pronouns before the verb:

σου = “to you / your” (indirect object, genitive)
τη / την = “her / it” (direct object, accusative)

Θα σου τη στείλω literally is “I will to-you it send” → “I will send it to you.”

The order of clitic pronouns is fixed:

Genitive pronoun: μου, σου, του, της, μας, σας, τους
Accusative pronoun: τον, την/τη, το, τους, τις, τα

So:

Correct: θα σου τη στείλω
Not correct: θα τη σου στείλω

You could also avoid pronouns and say:

Θα στείλω την άσκηση σε σένα. = I will send the exercise to you.

But in normal speech, native speakers strongly prefer the clitic pronouns: θα σου τη στείλω.

Where is the word for “I” in this sentence?

The subject pronoun “I” (εγώ) is not written, because in Greek it is usually implied by the verb ending.

στείλω = (I) will send
εξηγήσω = (I) will explain

So:

θα σου τη στείλω = (εγώ) θα σου τη στείλω
θα σου την εξηγήσω = (εγώ) θα σου την εξηγήσω

You only add εγώ if you want to emphasize I:

Εγώ θα σου τη στείλω ξανά. = I will send it to you again (not someone else).

What form is βρεις, and why not βρίσκεις?

βρεις is the aorist subjunctive of the verb βρίσκω (“to find”).

Present indicative: βρίσκεις = you find / you are finding
Aorist subjunctive: βρεις = you (may) find (once, as a complete event)

After αν (“if”), Greek normally uses the subjunctive, not the present indicative, when talking about a possible event:

Αν δεν τη βρεις… = If you don’t (manage to) find it…

Using βρίσκεις here would be ungrammatical:

✗ Αν δεν τη βρίσκεις, θα σου τη στείλω… (wrong in this meaning)

So the pattern is:

Αν
- subjunctive (here: δεν τη βρεις)
Main clause with θα
- verb (here: θα σου τη στείλω)

What does αν do here, and how is it used?

αν means “if” and introduces a conditional clause:

Αν δεν τη βρεις, → If you don’t find it,
θα σου τη στείλω ξανά… → I’ll send it to you again…

In Modern Greek:

αν is followed by a subjunctive verb: αν (δεν) τη βρεις
The result clause typically uses θα
- verb: θα σου τη στείλω

You might also see εάν (more formal) or άμα (more colloquial), which work similarly:

Εάν δεν τη βρεις…
Άμα δεν τη βρεις…

Why is θα used here, and why do στείλω and εξηγήσω look different from στέλνω and εξηγώ?

θα is the marker of the future in Modern Greek. The future is formed as:

θα
- subjunctive form of the verb.

The verbs have two basic aspects:

Present stem (ongoing / repeated action):
- στέλνω = I send / I am sending
- εξηγώ = I explain / I am explaining
Aorist stem (single, complete action):
- στείλω = (that) I send (once)
- εξηγήσω = (that) I explain (once)

With θα:

θα στέλνω = I will be sending (over time, repeatedly)
θα στείλω = I will send (once, complete act)
θα εξηγώ = I will be explaining
θα εξηγήσω = I will explain (once, from start to finish)

In the sentence, we want one complete future action (send it once, explain it once), so we use:

θα σου τη στείλω
θα σου την εξηγήσω

Do we really need to repeat θα before σου την εξηγήσω?

No, you don’t have to. Both are possible:

…θα σου τη στείλω ξανά και θα σου την εξηγήσω αργά.
…θα σου τη στείλω ξανά και σου την εξηγήσω αργά.

Repeating θα is very common and clear, and many speakers naturally keep it.
Omitting the second θα is also grammatically correct in informal speech, but in writing you will more often see θα repeated for clarity:

Same subject, same future: repeating θα just makes the structure more obvious.

Could we say θα σου τη ξαναστείλω instead of θα σου τη στείλω ξανά? Is there a difference?

Yes, both are correct:

Θα σου τη στείλω ξανά.
Θα σου τη ξαναστείλω.

They both mean “I’ll send it to you again.”

In (1) ξανά is a free adverb after the verb phrase.
In (2) ξανά is attached to the verb as a prefix: ξανα-στείλω → ξαναστείλω.

Sentence (2) often sounds a bit more compact and idiomatic in everyday speech.
There is no real change in meaning here; both are neutral “again,” not necessarily annoyed or emotional.

Does αργά mean “slowly” or “late” in this sentence?

αργά is the adverb from αργός and has two main uses:

Time: late
- Ήρθε αργά. = He/She came late.
- Αργά το βράδυ. = Late at night.
Manner: slowly / in a slow, careful way
- Μίλα αργά. = Speak slowly.

In θα σου την εξηγήσω αργά, the meaning is the second one:
“I will explain it to you slowly / carefully / at a slow pace,” so that you can understand.

Why is the order δεν τη βρεις and not τη δεν βρεις? Where do δεν and the pronoun go?

Greek has a fairly strict order for negation + clitic pronouns + verb in simple forms:

Negation: δεν (or μη(ν) in some constructions)
Clitic pronouns (σου, του, τη(ν), το, etc.)
Verb

So:

Αν δεν τη βρεις = If you don’t find it
✗ Αν τη δεν βρεις (wrong order)

Similarly, with θα:

Θα σου τη στείλω.
- θα
  - σου τη (clitic cluster) + στείλω (verb)

You can’t separate the clitic pronouns from the verb, and δεν must come before the whole clitic+verb unit:

Δεν σου τη στέλνω. = I’m not sending it to you.
✗ Σου δεν τη στέλνω (incorrect)

Can we replace σου with σε σένα in this sentence? How does that change the feel?

Yes, you can replace the clitic σου with the stressed phrase σε σένα:

Θα σου τη στείλω ξανά.
Θα τη στείλω ξανά σε σένα.

Both mean “I’ll send it to you again,” but:

σου is unstressed, clitic and the most natural everyday choice.
σε σένα is stressed and can add emphasis (“to you (specifically)”) or be used when the clitic is impossible for some reason.

In this particular sentence, natives would overwhelmingly say:

Θα σου τη στείλω ξανά και θα σου την εξηγήσω αργά.

using σου both times.