Learn Hardcore Greek: Βάζω το τηλέφωνό μου μέσα σε μια τσάντα.

Βάζω is the present tense, 1st person singular form of the verb βάζω = “to put / to place.”
So βάζω on its own means “I put” or “I am putting” (Greek uses the same present form for both simple and continuous meanings, depending on context).

Why is there no “I” (εγώ) in the Greek sentence?

Greek usually drops subject pronouns because the verb ending already shows the person.

βάζω can only mean “I put”, so εγώ is not needed.
You could say Εγώ βάζω το τηλέφωνό μου… for emphasis (like “I put my phone…”), but in neutral sentences it’s normally omitted.

Why is it το τηλέφωνό μου and not just τηλέφωνό μου?

In Greek, most singular countable nouns need an article (definite or indefinite) in normal sentences.
Here το is the definite article, neuter singular (“the”), agreeing with το τηλέφωνο (“the phone”).
So:

το τηλέφωνό μου = “my phone” (literally “the phone my”).
Saying only τηλέφωνό μου without το is generally not standard in this kind of sentence.

Why does τηλέφωνο become τηλέφωνό with an accent on the last syllable?

The basic word is το τηλέφωνο (stress on -λέ-, third syllable from the end).
When a proparoxytone word (stress on the third-from-last syllable) is followed by a clitic like μου (“my”), Greek spelling rules add a second accent on the last syllable:

το τηλέφωνο → το τηλέφωνό μου

This keeps the stress within the last three syllables of the whole phrase τηλέφωνό μου.
So the double accent is a normal spelling accent rule when adding μου, σου, etc. to words like τηλέφωνο.

What gender and case is το τηλέφωνό μου, and why?

τηλέφωνο is neuter, so its article is το.
In the sentence it is a direct object (“I put my phone”), so it is in the accusative case: το τηλέφωνό μου.

Neuter nouns ending in -ο (like το βιβλίο, το σπίτι, το τηλέφωνο) are very often neuter and take το in the singular accusative.

Why is the possessive μου placed after the noun instead of before, like in English?

In Greek, possessive pronouns (μου, σου, του, της, μας, σας, τους) normally follow the noun:

το τηλέφωνό μου = literally “the phone my”

This is the standard structure.
You can use forms like δικό μου before or after the noun for emphasis (e.g. το δικό μου τηλέφωνο = “my own phone”), but the simple possessive almost always comes after the noun.

Why do we have both μέσα and σε? Isn’t one preposition enough?

Here, μέσα is an adverb meaning “inside”, and σε is the basic preposition “in / into / to”.
Together μέσα σε literally means “inside in/into”, but idiomatically just “inside (something)”:

μέσα σε μια τσάντα = “inside a bag / into a bag”

You can often use only σε (στην τσάντα) and the meaning “into the bag” is still clear; μέσα just emphasizes the idea of being inside, not just towards.

Could I say Βάζω το τηλέφωνό μου στην τσάντα instead? What’s the difference?

Yes, that is correct and very natural:

Βάζω το τηλέφωνό μου στην τσάντα. = “I put my phone in the bag.”

Differences:

στην τσάντα = “in the bag” (a specific bag; definite article).
σε μια τσάντα = “in a bag” (any bag, not specified; indefinite article).
Adding μέσα (μέσα στην τσάντα) strengthens the idea of inside the bag.

So your original sentence emphasizes any bag and the inside of it.

Why is it σε μια τσάντα and not σε ένα τσάντα?

The indefinite article has different forms for gender:

ένας (masculine), μία / μια (feminine), ένα (neuter).

The noun τσάντα is feminine, so its accusative singular with σε uses the feminine form:

σε μία / σε μια τσάντα = “in a bag”

Ένα is neuter; it would be used with neuter nouns, e.g. σε ένα σπίτι (“in a house”).

Why is τσάντα in the accusative case?

Preposition σε normally takes the accusative case.
So:

η τσάντα (nominative) → μια τσάντα in accusative after σε: σε μια τσάντα.

Even when the English feels like a “location” (“in the bag”), Greek still uses σε + accusative, not dative (modern Greek no longer has a separate dative case).

Is the word order fixed? Could I say Βάζω μέσα σε μια τσάντα το τηλέφωνό μου?

Yes, that order is grammatically correct:

Βάζω μέσα σε μια τσάντα το τηλέφωνό μου.

Greek word order is fairly flexible. The most neutral here is probably:

Βάζω το τηλέφωνό μου μέσα σε μια τσάντα.

Moving elements (like μέσα σε μια τσάντα) earlier or later can change emphasis slightly, but the sentence remains understandable.

What’s the difference between τηλέφωνο and κινητό? Could I say Βάζω το κινητό μου…?

τηλέφωνο = “telephone / phone” in general (often landline or just the device).
κινητό (τηλέφωνο) = “mobile phone / cell phone.”

In everyday speech, people often just say το κινητό for “my phone (my mobile)”.
So you can absolutely say:

Βάζω το κινητό μου μέσα σε μια τσάντα. = “I put my (mobile) phone in a bag.”