Learn Hardcore Greek: Χρησιμοποιώ δυνατό κωδικό για τον λογαριασμό μου στο ίντερνετ. - I use a strong password for my account on the internet.

Χρησιμοποιώ ends in -ώ, which marks 1st person singular → “I use”.
Adding εγώ (I) is only for emphasis or contrast:
Εγώ χρησιμοποιώ δυνατό κωδικό… = I use a strong password (implying others maybe don’t).

So the basic sentence Χρησιμοποιώ δυνατό κωδικό… already means “I use a strong password …” without needing εγώ.

What exactly does χρησιμοποιώ mean, and what tense is it?

Χρησιμοποιώ means “I use”.

Grammatically:

It is present tense, 1st person singular, active voice.
In Greek, the present tense usually covers both English present simple and present continuous:
- Χρησιμοποιώ δυνατό κωδικό can mean:
  - I use a strong password (in general / habitually)
  - I am using a strong password (right now)

The basic dictionary form is also χρησιμοποιώ (1st person singular present).
Past tense would be χρησιμοποίησα = I used.

Why is it δυνατό κωδικό and not δυνατός κωδικός?

The form of the adjective changes to agree with the case, gender, and number of the noun.

The noun κωδικός (password/code) is:
- masculine
- singular
In the sentence it is the direct object (what I use), so it’s in the accusative case:
- nominative: ο κωδικός (subject)
- accusative: τον κωδικό (object)

The adjective δυνατός must match that:

nominative masculine singular: δυνατός κωδικός
accusative masculine singular: δυνατό κωδικό

Because we need the accusative for the object, we say δυνατό κωδικό.

In English we say “a strong password”. Why is there no “a” before δυνατό κωδικό?

Modern Greek does not have a true indefinite article like English “a / an” in most normal uses.

You often just omit it:
Χρησιμοποιώ δυνατό κωδικό ≈ I use a strong password.

Greek has ένας / μία / ένα, which can act a bit like “a/an”, but they are not required:

Χρησιμοποιώ έναν δυνατό κωδικό. – also correct, a bit more specific/emphatic: I use one strong password / a particular strong password.

In many everyday sentences, especially with objects mentioned for the first time, the article is simply left out, as in your example.

Why is it τον λογαριασμό and not το λογαριασμό or του λογαριασμού?

Because λογαριασμός (account / bill) is masculine, and here it is in the accusative singular after the preposition για.

Forms of the noun:

nominative: ο λογαριασμός (subject)
accusative: τον λογαριασμό (object or after many prepositions)
genitive: του λογαριασμού (of the account)

So:

τον λογαριασμό = the account (accusative) → correct after για
το λογαριασμό would use the neuter article (το), which is wrong for a masculine noun.
του λογαριασμού is genitive (“of the account”), not used here.

What exactly is μου in τον λογαριασμό μου, and why is it after the noun?

Μου here is the unstressed possessive pronoun meaning “my”.

In Greek, these short possessive pronouns usually come after the noun:
- ο λογαριασμός μου = my account
- το σπίτι σου = your house
- η τσάντα της = her bag

They are clitics (unstressed little words) and cannot stand alone.

For emphasis or contrast, Greek uses a different structure:

ο δικός μου λογαριασμός = my own account / my account (as opposed to someone else’s)

So in normal, neutral speech, noun + μου is the standard way to say “my …”.

What does για mean here, and why does it use the accusative τον λογαριασμό?

Για is a preposition that often means “for” or “about”.

In your sentence:

δυνατό κωδικό για τον λογαριασμό μου = a strong password for my account

Prepositions in Greek usually require a specific case.
Για almost always takes the accusative case, so the noun after it must be in the accusative:

για τον λογαριασμό (μου) – for the account (my account)
για το παιδί – for the child
για την πόλη – for the city

What is στο in στο ίντερνετ, and why do we use it?

Στο is a contraction of the preposition σε + the definite article το:

σε + το → στο

It usually means “in the / on the / at the”, depending on context.

Ίντερνετ (“internet”) in Greek is treated as a neuter indeclinable noun, so its article is το:

το ίντερνετ = the internet
στο ίντερνετ = on the internet / online

So:

στο ίντερνετ literally = in/on the internet

You could also hear στο διαδίκτυο, which is a more “Greek” word for internet, but στο ίντερνετ is very common and natural.

Why isn’t it δυνατός κωδικός για ο λογαριασμός μου with ο?

Because after για you cannot use the nominative form ο λογαριασμός.
You need the accusative:

nominative: ο λογαριασμός (subject)
accusative: τον λογαριασμό (object / after prepositions like για)

Prepositions in Greek are followed by oblique cases (usually accusative in Modern Greek), not the nominative.

So:

❌ για ο λογαριασμός μου – incorrect
✅ για τον λογαριασμό μου – correct

Is the word order fixed? Can I move parts of the sentence around?

Greek word order is fairly flexible, especially compared to English.
Your version:

Χρησιμοποιώ δυνατό κωδικό για τον λογαριασμό μου στο ίντερνετ.

Other natural variants (with slightly different emphasis) include:

Για τον λογαριασμό μου στο ίντερνετ χρησιμοποιώ δυνατό κωδικό.
(Emphasis on for my internet account.)
Δυνατό κωδικό χρησιμοποιώ για τον λογαριασμό μου στο ίντερνετ.
(Emphasis on strong password.)

As long as the endings and prepositions are correct, the basic meaning stays clear.
However, the original order (verb + object + prepositional phrase) is very natural and neutral in tone.

How would the sentence change for “we use”, “you (plural) use”, or “they use”?

You keep the rest of the sentence the same and change only the verb ending.

Present tense of χρησιμοποιώ:

(εγώ) χρησιμοποιώ – I use
(εσύ) χρησιμοποιείς – you (singular) use
(αυτός/αυτή/αυτό) χρησιμοποιεί – he/she/it uses
(εμείς) χρησιμοποιούμε – we use
(εσείς) χρησιμοποιείτε – you (plural / formal) use
(αυτοί/αυτές/αυτά) χρησιμοποιούν / χρησιμοποιούνε – they use

So:

Χρησιμοποιούμε δυνατό κωδικό για τον λογαριασμό μας στο ίντερνετ. – We use a strong password for our internet account.
Χρησιμοποιείτε δυνατό κωδικό για τον λογαριασμό σας στο ίντερνετ. – You (plural/formal) use a strong password…
Χρησιμοποιούν δυνατό κωδικό για τον λογαριασμό τους στο ίντερνετ. – They use a strong password…

Is δυνατός κωδικός the usual way to say “strong password” in Greek, or is there a more common expression?

Δυνατός κωδικός is understandable and acceptable in everyday speech, but in more technical or formal contexts, Greek often prefers:

ισχυρός κωδικός – strong password
ισχυρός κωδικός πρόσβασης – strong access password

So:

Everyday, casual: δυνατός κωδικός – sounds fine.
More standard/technical: ισχυρός κωδικός (πρόσβασης).

In your sentence, Χρησιμοποιώ δυνατό κωδικό για τον λογαριασμό μου στο ίντερνετ, a native speaker would understand perfectly. In written security instructions, you’re more likely to see ισχυρό κωδικό.