Learn Hardcore Greek: Θέλω να ξεκαθαρίσω ότι είμαι απλώς κουρασμένος. - I want to make it clear that I am just tired.

In Greek, verbs like θέλω (I want), μπορώ (I can), πρέπει (I must) normally take another verb introduced by να.
So θέλω να ξεκαθαρίσω literally is “I want that I (should) clarify”.
The να marks a subordinate verb (subjunctive-type clause). You cannot say ✱θέλω ξεκαθαρίσω; the να is required.

Why is it ξεκαθαρίσω and not ξεκαθαρίζω after θέλω να?

Ξεκαθαρίσω is the aorist subjunctive; ξεκαθαρίζω is present.

θέλω να ξεκαθαρίσω = “I want to clarify (this) once / make it clear now.”
θέλω να ξεκαθαρίζω would mean “I want to be clarifying (habitually, repeatedly).”
Because the speaker is talking about one specific act of clarification, the aorist ξεκαθαρίσω is the natural choice.

Is ξεκαθαρίσω a past tense? It looks like the aorist form I learned for past.

The form you see (aorist stem) is used both:

as simple past indicative: ξεκαθάρισα = I clarified
and as aorist subjunctive: να ξεκαθαρίσω = (that) I clarify (once).
Here, because it follows να, it is subjunctive, not past. Greek reuses the same stem for these two functions; the context (να) tells you which it is.

What exactly does ξεκαθαρίζω mean? Is it just “clarify”?

Yes, ξεκαθαρίζω means “to make clear, clarify, sort out, straighten out.”
Literally, it’s ξε- (a prefix meaning “out, off, completely”) + καθαρίζω (“to clean”). So it’s like “to clean up/clear up” an issue.
In this sentence, να ξεκαθαρίσω = “to make it clear / to clarify.”

What’s the difference between ότι and πως here? Could I say Θέλω να ξεκαθαρίσω πως είμαι απλώς κουρασμένος?

Yes, you can. In modern Greek, after verbs of saying/thinking, ότι and πως both commonly mean “that”:

ξεκαθαρίζω ότι…
ξεκαθαρίζω πως…
In everyday speech they’re largely interchangeable here. Ότι is slightly more neutral/standard; πως may feel a bit more informal or conversational in some contexts, but both are fine.

How is ότι different from ό,τι with a comma?

ότι (no comma) is a conjunction meaning “that” introducing a clause: Ξέρω ότι είσαι εδώ = I know that you are here.
ό,τι (with comma) is an indefinite pronoun, meaning “whatever / anything that”: Κάνε ό,τι θέλεις = Do whatever you want.
In this sentence it must be ότι, because it introduces the statement είμαι απλώς κουρασμένος (“that I am simply tired”).

What does απλώς mean exactly? Is it “just” or “simply” or “only”?

Απλώς means “simply / just (in the sense of merely)”.
Here είμαι απλώς κουρασμένος = “I’m just / only / simply tired (nothing more).”
It downplays the situation: I’m not angry, sick, etc.—just tired.

How is απλώς different from μόνο and from απλά?

μόνο is mainly “only” in a limiting sense: Έχω μόνο ένα ευρώ = I have only one euro.
απλώς is “simply / merely”: Είμαι απλώς κουρασμένος = I’m simply/just tired.
απλά is originally the adverb “simply”, but in modern spoken Greek it often replaces απλώς: Είμαι απλά κουρασμένος (very common in speech).
In careful or written Greek, απλώς is preferred in this use, but απλά is extremely common in conversation.

Why is it κουρασμένος and not some other ending? What is it agreeing with?

Κουρασμένος is a masculine singular adjective meaning “tired”, agreeing with the (implied) masculine subject εγώ (I, male speaker).
If a woman were speaking, she would say είμαι κουρασμένη.
Plurals: είμαστε κουρασμένοι (we are tired – group with at least one male), είμαστε κουρασμένες (group of only women). Greek adjectives agree in gender and number with the noun/pronoun they describe.

Could the word order be Είμαι απλώς κουρασμένος, θέλω να ξεκαθαρίσω? Does that change the meaning?

You can say Είμαι απλώς κουρασμένος, θέλω να ξεκαθαρίσω, and it is grammatically fine.
The meaning is mostly the same, but the original order
Θέλω να ξεκαθαρίσω ότι είμαι απλώς κουρασμένος
sounds more natural and emphasizes the intention to clarify first, then the content of that clarification. The alternative sounds a bit more casual and less tightly structured.

Can απλώς go in a different place, like είμαι κουρασμένος απλώς or απλώς είμαι κουρασμένος?

Yes, Greek adverbs move around fairly freely:

Είμαι απλώς κουρασμένος (most typical here)
Απλώς είμαι κουρασμένος (emphasis on “just”: I’m just tired)
Είμαι κουρασμένος απλώς (less common, more “tagged on” at the end).
All are understandable; the chosen position slightly changes the rhythm and emphasis, but not the basic meaning.

Is απλώς an adverb or an adjective?

Here απλώς is an adverb modifying the adjective κουρασμένος (“tired”).
It comes from the adjective απλός (“simple”), but with the -ως ending it functions as an adverb (“simply”).
So the structure is: είμαι (copula verb) + κουρασμένος (adjective) + απλώς (adverb).

How formal or informal does this whole sentence sound? Are there more formal alternatives to ξεκαθαρίσω?

Θέλω να ξεκαθαρίσω ότι είμαι απλώς κουρασμένος is neutral and appropriate in most contexts, from everyday speech to semi-formal writing.
A bit more formal would be Θέλω να διευκρινίσω ότι είμαι απλώς κουρασμένος (using διευκρινίζω = “to clarify, to specify”).
More casual speech might drop ότι and say Θέλω να ξεκαθαρίσω, είμαι απλώς κουρασμένος or even just Απλώς είμαι κουρασμένος.

How do you pronounce each word in this sentence?

Approximate pronunciation (stress in CAPITALS):

Θέλω → THEH-lo (Θ like English “th” in this)
να → na (short “a” as in father)
ξεκαθαρίσω → kse-ka-tha-REE-so (again θ like “th” in this)
ότι → O-tee
είμαι → EE-meh
απλώς → ap-LOHS (final ς like “s”)
κουρασμένος → koo-raz-ME-nos (Greek ου = “oo” as in food).