Sunt absolut sigur.

Because Romanian often drops the subject pronoun when it is clear from the verb ending.

• sunt = I am / they are
• In this sentence, context usually makes it clear that it means I am

So Sunt absolut sigur is a natural way to say I am absolutely sure.

You can also say:

• Eu sunt absolut sigur = I am absolutely sure

But eu is usually added only for emphasis, contrast, or clarity.

Sunt is a form of the verb a fi, which means to be.

Here it means am:

• sunt = I am

It can also mean they are, depending on context:

• Sunt obosiți = They are tired
• Sunt sigur = I am sure or sometimes I’m sure, depending on the situation

So Romanian relies a lot on context when the subject is omitted.

Sigur is the adjective meaning sure, certain, or confident.

In Sunt absolut sigur, it agrees with the speaker.

If the speaker is:

• male: sigur
• female: sigură

So:

• Sunt absolut sigur = said by a man
• Sunt absolut sigură = said by a woman

This is a very common thing in Romanian: adjectives often change form depending on gender and number.

A woman would normally say:

• Sunt absolut sigură.

The only change is the final adjective:

• masculine: sigur
• feminine: sigură

Everything else stays the same.

Absolut means absolutely here. It strengthens sigur.

So:

• sigur = sure
• absolut sigur = absolutely sure

In this sentence, absolut works like an adverb, even though its form looks the same as the adjective absolute in English.

It does not change here for gender:

• Sunt absolut sigur.
• Sunt absolut sigură.

In both cases, absolut stays the same.

Yes. Sunt sigur is very common and natural.

Compare:

• Sunt sigur. = I’m sure.
• Sunt absolut sigur. = I’m absolutely sure.

So absolut simply adds extra emphasis.

The normal and most natural order is:

• Sunt absolut sigur.

Romanian word order is somewhat flexible, but not every variation sounds equally natural.

For example:

• Sunt sigur. = very natural
• Sunt absolut sigur. = very natural
• Absolut sigur sunt. = possible in special contexts, but marked or poetic/emphatic
• Sigur sunt. = possible in certain spoken contexts, but not the basic neutral form

So for learners, the best default is:

• Sunt absolut sigur.

Both can relate to certainty, but they are not always used in exactly the same way.

• sigur often means sure in everyday speech
• cert often means certain and can sound a bit more formal or objective in some contexts

For expressing I’m sure, Romanian commonly uses:

• Sunt sigur.

You may also hear:

• Sunt absolut convins. = I’m absolutely convinced.
• Sunt sigur de asta. = I’m sure of that.

So sigur is the most natural everyday choice here.

You add nu before the verb:

• Nu sunt absolut sigur. = I am not absolutely sure.
• Nu sunt sigur. = I’m not sure.

If the speaker is female:

• Nu sunt absolut sigură.

This is the standard way to negate the sentence.

A simple learner-friendly pronunciation guide would be:

• Sunt ≈ soont
• absolut ≈ ab-so-LOOT
• sigur ≈ see-GOOR

A few useful notes:

• Romanian u is usually like oo in food
• Romanian g in sigur is a hard g, like in go
• Stress is usually:
  • absolut
  • sigur

A rough full pronunciation:

• soont ab-so-LOOT see-GOOR

Usually, in this exact sentence, sigur means sure/certain, not safe.

Romanian sigur can sometimes relate to safety in other contexts, but with Sunt sigur, the normal meaning is:

• I am sure
• I am certain

If you want to talk about being safe, Romanian often uses other expressions depending on context, such as:

• Sunt în siguranță. = I am safe.

So in Sunt absolut sigur, the meaning is about certainty, not physical safety.

You change the verb and, if needed, the adjective ending:

• Suntem absolut siguri. = We are absolutely sure
  (for a group of males or a mixed group)
• Suntem absolut sigure. = We are absolutely sure
  (for a group of females)

So the pattern is:

• sunt = I am
• suntem = we are

And the adjective changes for number and gender:

• singular masculine: sigur
• singular feminine: sigură
• plural masculine/mixed: siguri
• plural feminine: sigure

It is neutral and works in both formal and informal situations.

• In conversation: Sunt absolut sigur.
• In a more formal setting: still perfectly fine

It is a standard, natural sentence. Nothing about it is slangy or unusually formal.

If you want an even stronger or slightly more formal-sounding version, you might also hear:

• Sunt pe deplin sigur. = I am fully sure
• Sunt absolut convins. = I am absolutely convinced

But Sunt absolut sigur is a very normal everyday sentence.