Υποθέτω ότι σήμερα είσαι πολύ κουρασμένος.

Υποθέτω means I suppose / I assume. In this sentence, it introduces a guess based on what the speaker thinks is probably true.

A very common alternative is νομίζω, which means I think. Compare:

• Υποθέτω ότι σήμερα είσαι πολύ κουρασμένος. = I suppose / I assume that you are very tired today.
• Νομίζω ότι σήμερα είσαι πολύ κουρασμένος. = I think that you are very tired today.

In everyday speech, νομίζω is often more common and slightly more neutral. Υποθέτω can sound a bit more like the speaker is making an assumption.

Ότι means that and introduces a subordinate clause:

• Υποθέτω = I suppose
• ότι σήμερα είσαι πολύ κουρασμένος = that today you are very tired

So the structure is:

• main verb + ότι + clause

Just like in English, that can sometimes be omitted in translation, but in Greek ότι is very normal here.

You may also see πως used in similar sentences:

• Υποθέτω πως σήμερα είσαι πολύ κουρασμένος.

In many everyday contexts, ότι and πως both mean that.

Είσαι is the 2nd person singular of είμαι (to be) in the present tense. It means you are.

So:

• είμαι = I am
• είσαι = you are
• είναι = he/she/it is

In this sentence:

• σήμερα είσαι πολύ κουρασμένος = today you are very tired

Greek often leaves out subject pronouns because the verb ending already shows the person.

Here, είσαι already tells you the subject is you (singular), so εσύ is not necessary.

• Σήμερα είσαι πολύ κουρασμένος. = Today you are very tired.
• Σήμερα εσύ είσαι πολύ κουρασμένος. = more emphatic, like You are the one who is very tired today or You, today, are very tired

So the pronoun is usually omitted unless there is emphasis or contrast.

Κουρασμένος is an adjective meaning tired. It changes form to agree with the person being described in gender, number, and case.

Here it is:

• masculine singular nominative: κουρασμένος

That means the speaker is talking to one male person.

Other forms include:

• κουρασμένη = tired, for one female
• κουρασμένο = tired, neuter singular
• κουρασμένοι = tired, masculine plural
• κουρασμένες = tired, feminine plural

So if speaking to a woman, you would say:

• Υποθέτω ότι σήμερα είσαι πολύ κουρασμένη.

Historically, it comes from a participial form, but in everyday grammar learning it is best understood as an adjective meaning tired.

Greek often uses forms like this after είμαι:

• είμαι κουρασμένος = I am tired
• είσαι κουρασμένος = you are tired

So for practical purposes, treat it as an adjective that agrees with the noun or person it describes.

Πολύ means very here. It modifies the adjective κουρασμένος:

• πολύ κουρασμένος = very tired

This is a very common pattern in Greek:

• πολύ καλός = very good
• πολύ δύσκολο = very difficult
• πολύ όμορφη = very beautiful

Be careful: πολύ can also mean much / a lot, depending on context.

Σήμερα means today. In this sentence it comes before είσαι, which is a very natural position:

• Υποθέτω ότι σήμερα είσαι πολύ κουρασμένος.

But Greek word order is more flexible than English, so you could also hear:

• Υποθέτω ότι είσαι πολύ κουρασμένος σήμερα.

Both are natural. The difference is mainly one of emphasis or rhythm, not basic meaning.

Placing σήμερα earlier can make today feel slightly more foregrounded.

You only need to change the adjective so that it agrees with a feminine singular person:

• Υποθέτω ότι σήμερα είσαι πολύ κουρασμένη.

Everything else stays the same.

So:

• to a man: κουρασμένος
• to a woman: κουρασμένη

Yes, in informal spoken Greek, ότι is sometimes omitted:

• Υποθέτω σήμερα είσαι πολύ κουρασμένος.

However, this can sound a little less neat or slightly less standard depending on context. For learners, it is safest to keep ότι in sentences like this.

So the full version:

• Υποθέτω ότι σήμερα είσαι πολύ κουρασμένος.

is a very good model to use.

A rough pronunciation guide is:

• Υποθέτω ≈ ee-po-THE-to
• ότι ≈ O-ti
• σήμερα ≈ SEE-me-ra
• είσαι ≈ EE-se
• πολύ ≈ po-LEE
• κουρασμένος ≈ koo-ra-sme-NOS

A smoother approximation of the whole sentence:

• ee-po-THE-to O-ti SEE-me-ra EE-se po-LEE koo-ra-sme-NOS

A few useful pronunciation notes:

• υ here sounds like ee
• αι in είσαι sounds like e
• stress matters in Greek, so pay attention to the accented syllables:
  • υποθέτω
  • ότι
  • σήμερα
  • είσαι
  • πολύ
  • κουρασμένος

Greek accent marks show which syllable is stressed.

In this sentence:

• Υποθέτω → stress on θέ
• ότι → stress on ό
• σήμερα → stress on σή
• είσαι → stress on εί
• πολύ → stress on λύ
• κουρασμένος → stress on νός

Stress is important in Greek pronunciation and sometimes also helps distinguish words. So learners should try to memorize words together with their stress.

It is neutral and natural. The verb form είσαι shows that the speaker is addressing one person informally (the singular you).

If you were addressing someone formally or addressing more than one person, Greek would use είστε instead:

• Υποθέτω ότι σήμερα είστε πολύ κουρασμένος.
  formal singular, to a man
• Υποθέτω ότι σήμερα είστε πολύ κουρασμένη.
  formal singular, to a woman
• Υποθέτω ότι σήμερα είστε πολύ κουρασμένοι.
  plural, to a group including men or mixed group
• Υποθέτω ότι σήμερα είστε πολύ κουρασμένες.
  plural, to a group of women

So the original sentence is singular and informal.