Learn Hardcore Greek: Σήμερα είμαι πολύ σίγουρος για την απόφασή μου.

Σήμερα – today
είμαι – I am (1st person singular of είμαι, to be)
πολύ – very / a lot (here: very)
σίγουρος – sure, certain (masculine form of the adjective)
για – for / about (here: about)
την – the (feminine singular, accusative case)
απόφασή – decision (the noun απόφαση, here in the accusative with shifted stress)
μου – my (unstressed/“weak” form of εγώ, functioning as a possessive: my decision)

So the structure is literally: Today I-am very sure about the my-decision.

Why is σίγουρος and not another ending, like σίγουρη or σίγουρο?

In Greek, adjectives must agree with the noun they describe, or with the gender of the person they describe.

Here, σίγουρος describes the speaker (the subject I), whose grammatical gender is assumed to be masculine.

If the speaker is male:
- Είμαι πολύ σίγουρος. – I am very sure. (masculine)
If the speaker is female:
- Είμαι πολύ σίγουρη. – I am very sure. (feminine)
If the subject were a neuter noun (e.g. το παιδί – the child):
- Το παιδί είναι πολύ σίγουρο. – The child is very sure. (neuter)

So σίγουρος is masculine; σίγουρη is feminine; σίγουρο is neuter. The sentence as given assumes a male speaker.

Why do we say για την απόφασή μου and not just την απόφασή μου or απόφασή μου?

The preposition για is required here because in Greek, when you say sure/certain *about something, you normally use *για:

είμαι σίγουρος για κάτι – I’m sure about something.
είμαι σίγουρη για την απόφασή μου – I’m sure about my decision.

Without για, the phrase την απόφασή μου would sound like a direct object of some verb, but είμαι (I am) does not take a direct object in that way.

So:

Σήμερα είμαι πολύ σίγουρος για την απόφασή μου. ✅
Σήμερα είμαι πολύ σίγουρος την απόφασή μου. ❌ (ungrammatical)

You need για to express the idea of being sure about something.

Why do we need the article την before απόφασή μου? In English we don’t say “the my decision”.

In Greek, it is normal (and very common) to have:

article + noun + possessive pronoun

So την απόφασή μου literally is the decision my, but it corresponds to English “my decision”.

Patterns like these are standard:

το σπίτι μου – my house (literally the house my)
η μητέρα σου – your mother (literally the mother your)
τον φίλο μας – our friend (accusative masculine: the friend our)

Here:

για την απόφασή μου
- για – about
- την – the (feminine, accusative, required after για)
- απόφασή – decision (in accusative)
- μου – my

So the article την is grammatically required because:

Greek normally uses the article with possessive pronouns in this pattern, and
για is followed by the accusative, and the article is what marks that case clearly.

Why does απόφαση become απόφασή with the accent on the last syllable?

The base word is:

η απόφαση – the decision (accent on the first syllable: Α-ΠΟ-φα-ση)

But in the sentence we have:

την απόφασή μου

The accent moved to the last syllable of απόφασή. This happens because of a rule involving enclitics (unstressed words) like μου.

Rule (simplified):
When a word with three or more syllables is followed by an enclitic (such as μου, σου, του, της, μας, σας, τους), an extra stress is often added to the last syllable of the main word.

So:

η απόφαση (alone)
την απόφασή μου (followed by enclitic μου, so accent shifts/gets duplicated on the last syllable)

You’ll see the same pattern with other words:

η άσκηση → την άσκησή μου – my exercise
η σελίδα → τη σελίδα μου (no extra accent; only three syllables total)

In την απόφασή μου, the extra accent shows how the word is pronounced when μου is attached.

Why is απόφασή in the accusative case here? How can I tell?

The preposition για in this meaning (about / for) always takes the accusative case in modern Greek.

The noun η απόφαση (decision) changes form in the different cases:

Nominative (subject): η απόφαση – the decision
Accusative (object / after prepositions like για): την απόφαση – the decision

In the sentence:

για την απόφασή μου
- The article την clearly shows the accusative (feminine singular),
- The noun απόφασή is in the accusative, agreeing with την.

So απόφασή is accusative because:

It follows the preposition για, and
It’s the object of that preposition: about my decision.

Can I change the word order, for example: Σήμερα πολύ σίγουρος είμαι για την απόφασή μου or Είμαι σήμερα πολύ σίγουρος…?

Greek word order is fairly flexible, but some versions sound more natural than others.

Most natural options here:

Σήμερα είμαι πολύ σίγουρος για την απόφασή μου. (neutral)
Είμαι σήμερα πολύ σίγουρος για την απόφασή μου. (still natural; slight emphasis on “today”)
Είμαι πολύ σίγουρος σήμερα για την απόφασή μου. (emphasis that today you’re sure, maybe not on other days)

Unnatural or unusual:

Σήμερα πολύ σίγουρος είμαι για την απόφασή μου. – Grammatically possible, but sounds poetic or overly dramatic in everyday speech.

The default, neutral-sounding choice is exactly the one you were given:

Σήμερα είμαι πολύ σίγουρος για την απόφασή μου.

What is the difference between πολύ σίγουρος and just σίγουρος? Could I say Σήμερα είμαι σίγουρος για την απόφασή μου?

Yes, you can definitely say:

Σήμερα είμαι σίγουρος για την απόφασή μου.

That would mean:

Today I am sure about my decision. (just sure)

Adding πολύ strengthens the meaning:

πολύ σίγουρος – very sure or really sure

So:

Σήμερα είμαι σίγουρος για την απόφασή μου. – I’m sure.
Σήμερα είμαι πολύ σίγουρος για την απόφασή μου. – I’m very sure / absolutely certain.

πολύ here is an adverb modifying the adjective σίγουρος.

Why is it πολύ (with -υ) and not πολλή (with -ή)?

Greek has two forms that look similar:

πολύ – adverb or neuter adjective, meaning very, a lot
πολλή / πολύς / πολύ – adjective meaning many / much (with gender and case changes)

In πολύ σίγουρος, πολύ is an adverb modifying the adjective σίγουρος:

πολύ σίγουρος – very sure

As an adverb, it stays πολύ and does not change for gender or number.

Compare:

Έχω πολλή δουλειά. – I have a lot of work. (adjective, feminine: πολλή
- δουλειά)
Είμαι πολύ κουρασμένος. – I am very tired. (adverb: πολύ
- adjective)

So here πολύ is the correct adverb form meaning very.

How would the sentence change if the speaker were a woman, or if we were talking about “our decision” instead of “my decision”?

Female speaker (only the adjective changes to feminine):

Σήμερα είμαι πολύ σίγουρη για την απόφασή μου.
- σίγουρη – feminine form of sure

“Our decision” instead of “my decision”:

Masculine speaker:
- Σήμερα είμαι πολύ σίγουρος για την απόφασή μας. – Today I am very sure about our decision.
Female speaker:
- Σήμερα είμαι πολύ σίγουρη για την απόφασή μας.

Only the possessive pronoun at the end changes:

μου – my
σου – your (singular)
του / της – his / her
μας – our
σας – your (plural / formal)
τους – their

How do I pronounce σίγουρος and απόφασή (any tips for an English speaker)?

Pronunciation breakdown (stress in bold):

Σήμερα – ΣΗ-με-ρα (SEE-meh-ra)
είμαι – ΕΙ-μαι (EE-me)
πολύ – πο-ΛΥ (po-LEE)
σίγουρος – ΣΙ-γου-ρος (SEE-ghoo-ros)
- γ before ου is a soft “gh”, like French g in garçon but further back.
για – ΓΙΑ (ya) – sounds like “ya”
την – ΤΗΝ (teen)
απόφασή – α-ΠΟ-φα-ΣΗ here effectively has strong stress on the last syllable (a-PO-fa-SEE), because of the enclitic μου.
μου – ΜΟΥ (moo)

Put together more naturally:

ΣΗ-me-ra EE-me po-LEE SEE-ghoo-ros ya teen a-PO-fa-SEE moo

Biggest points for English speakers:

All vowels are pure and short; each written vowel is pronounced.
The stress mark (΄) tells you which syllable to emphasize.
γ
- ου → a soft gh sound, not like English hard “g” in go.