Learn Hardcore Greek: Σήμερα πρέπει να τακτοποιήσω λίγο το δωμάτιό μου.

It is basically impersonal: it only appears as πρέπει, not πρέπω, πρέπει, πρέπει… like a normal conjugated verb.
The person (I, you, he etc.) is shown in the verb that follows να, not in πρέπει.

In the sentence:

πρέπει να τακτοποιήσω… = I have to tidy…
(the -ω/ -σω ending of τακτοποιήσω shows “I”)

You can’t say “εγώ πρέπειω” or anything like that; it’s always πρέπει + να + verb.

Why do we need να? Is it like the English “to”?

Yes, να often corresponds to English “to” when you say things like “I want to tidy”, “I have to tidy”.

Modern Greek has no infinitive form like English “to tidy”. Instead it uses:

να
- a subjunctive verb form

So:

πρέπει να τακτοποιήσω ≈ I must / I have to tidy (up)

Other examples:

Θέλω να φάω. = I want to eat.
Μπορώ να πάω; = Can I go?

What verb form is τακτοποιήσω, and how is it different from τακτοποιώ?

Both come from the verb τακτοποιώ (“to tidy, to put in order”).

τακτοποιώ = present tense, indicative, 1st person singular
→ I tidy / I am tidying
τακτοποιήσω = aorist subjunctive, 1st person singular
→ used after να, θα, ίσως, etc., usually for a single, complete action

You can think of να τακτοποιήσω as “(for me) to tidy (once / get it done)” rather than an ongoing or repeated action.

Could I say Σήμερα πρέπει να τακτοποιώ λίγο το δωμάτιό μου instead? What’s the difference?

You can say it, and it is grammatically correct, but the meaning changes:

πρέπει να τακτοποιήσω → I have to tidy my room (this time, get it done)
A specific, more “one-off” action.
πρέπει να τακτοποιώ → I have to be tidying / keep tidying / regularly tidy my room.
This suggests a habit or ongoing duty, like a rule.

In your original sentence, you mean “Today I have to tidy my room (now, once)”, so τακτοποιήσω is the natural choice.

What does λίγο do here, and where can it go in the sentence?

λίγο means “a little / a bit” and it modifies the verb, not the room.

Σήμερα πρέπει να τακτοποιήσω λίγο το δωμάτιό μου
≈ Today I have to tidy my room a bit.

Common positions:

να τακτοποιήσω λίγο το δωμάτιό μου ✔
να τακτοποιήσω το δωμάτιό μου λίγο ✔ (slightly more emphasis at the end)

You wouldn’t normally put λίγο directly in front of the noun here (e.g. λίγο το δωμάτιό μου) to mean “my room a little”; it’s understood as “tidy a bit” or “tidy a little”.

Why is μου after δωμάτιο and not before, like in English “my room”?

In Greek, the usual order is:

article + noun + possessive pronoun

So:

το δωμάτιό μου = my room
(literally “the room my”)

Other examples:

το βιβλίο μου = my book
η μητέρα σου = your mother
ο φίλος του = his / its friend

You can see μου δωμάτιο or δωμάτιο μου only in poetry or very marked styles; in everyday modern Greek, το δωμάτιό μου is the normal order.

Why do we need the article το with δωμάτιό μου? English doesn’t say “the my room”.

Greek normally uses the definite article together with possessive pronouns:

το δωμάτιό μου = my room
η δουλειά σου = your job
τα παιδιά μας = our children

Leaving the article out (δωμάτιό μου) is either:

wrong in standard Greek, or
sounds very poetic / archaic.

So in normal speech and writing, always use:

το + noun + possessive → το δωμάτιό μου

Why is there an accent on the last -ό in δωμάτιό?

The base word is:

δωμάτιο (accent on μά: δωμάτιο)

When a word stressed on the antepenultimate syllable (third from the end) is followed by a one-syllable enclitic like μου, σου, του, Greek spelling rules add a second accent on the last syllable:

δωμάτιο
- μου → δωμάτιό μου
άνθρωπος
- μου → άνθρωπός μου
δάσκαλος
- του → δάσκαλός του

So δωμάτιό has two accents: one on ά, one on ό. This keeps the stress pattern clear when the little pronoun μου is attached.

Can the word order change? For example: Πρέπει να τακτοποιήσω το δωμάτιό μου λίγο σήμερα. Is that still correct?

Yes, Greek word order is fairly flexible. All of these are correct:

Σήμερα πρέπει να τακτοποιήσω λίγο το δωμάτιό μου.
Σήμερα πρέπει να τακτοποιήσω το δωμάτιό μου λίγο.
Πρέπει σήμερα να τακτοποιήσω λίγο το δωμάτιό μου.
Πρέπει να τακτοποιήσω λίγο το δωμάτιό μου σήμερα.

Changes mainly affect emphasis:

Putting Σήμερα first highlights today.
Ending with σήμερα can sound like you’re adding “today” as an afterthought or emphasis at the end.

But all are natural and understandable.

How would the sentence change for our room or his room?

Just change the possessive pronoun:

my room → το δωμάτιό μου
your (sg.) room → το δωμάτιό σου
his room → το δωμάτιό του
her room → το δωμάτιό της
our room → το δωμάτιό μας
your (pl.) room → το δωμάτιό σας
their room → το δωμάτιό τους

So:

Σήμερα πρέπει να τακτοποιήσω λίγο το δωμάτιό μας.
= Today I have to tidy our room a bit.
Σήμερα πρέπει να τακτοποιήσω λίγο το δωμάτιό του.
= …his room.

Is τακτοποιήσω the only verb I can use? What’s its nuance compared to verbs like μαζέψω or καθαρίσω?

τακτοποιώ / τακτοποιήσω means to tidy up / arrange / put things in order. It focuses on putting things in their place, organizing.

Other options:

μαζέψω (from μαζεύω)
→ to pick up / gather / clear up (e.g. clothes, toys)
Σήμερα πρέπει να μαζέψω λίγο το δωμάτιό μου.
καθαρίσω (from καθαρίζω)
→ to clean (dusting, mopping, wiping)
Σήμερα πρέπει να καθαρίσω λίγο το δωμάτιό μου.
συμμαζέψω (from συμμαζεύω)
→ very close to “tidy up”, often both organizing and picking things up.

So in your original sentence, τακτοποιήσω suggests mainly organizing and putting things in order, not necessarily deep cleaning.