Sunt obosită azi, pentru că lucrez de dimineață.

Because the adjective has to agree with the speaker’s gender.

• obosit = masculine singular
• obosită = feminine singular

So a woman says Sunt obosită and a man says Sunt obosit.

Romanian often leaves out subject pronouns because the verb ending already shows who is doing the action.

• sunt already means I am
• so Sunt obosită is perfectly natural

You can add eu for emphasis or contrast:

• Eu sunt obosită, nu ea. = I’m tired, not her.

Sunt is the 1st person singular present form of a fi = to be.

So:

• sunt = I am

In this sentence, it links the speaker to the adjective:

• Sunt obosită = I am tired

Azi means today.

It is basically a shorter, very common version of astăzi. In most everyday contexts, they mean the same thing.

• azi = today
• astăzi = today

Both are correct, but azi often sounds a little more conversational.

Pentru că means because.

It introduces the reason for something:

• Sunt obosită azi, pentru că lucrez de dimineață.
• I’m tired today because I’ve been working since this morning.

It is one of the most common ways to say because in Romanian.

This is a very important difference between Romanian and English.

Romanian often uses the present tense with de + a time expression to show that:

• the action started in the past
• it is still continuing now

So:

• lucrez de dimineață literally looks like I work since morning
• but in natural English it is usually I have been working since this morning

This is normal Romanian usage.

Here, de dimineață means since this morning or from the morning onward.

In this sentence, it does not simply mean in the morning. It implies that the work started this morning and has continued until now.

So:

• lucrez de dimineață = I’ve been working since this morning

De dimineață is a common Romanian expression meaning since this morning / from early morning.

Romanian often uses:

• de
  • time expression

for ongoing actions:

• lucrez de două ore = I’ve been working for two hours
• te aștept de ieri = I’ve been waiting for you since yesterday

De la is more common when you mention a specific starting point:

• lucrez de la ora 8 = I’ve been working since 8 o’clock

So de dimineață is idiomatic and natural here.

Yes. Romanian word order is fairly flexible, although some versions sound more natural in certain contexts.

The original sentence is very natural:

• Sunt obosită azi, pentru că lucrez de dimineață.

You could also say:

• Azi sunt obosită, pentru că lucrez de dimineață.

That puts a bit more focus on azi = today.

The meaning stays basically the same.

Azi is an adverb of time. It tells you when the speaker is tired.

• Sunt obosită azi = I’m tired today

It modifies the whole statement, not just one word.

The main letters English speakers usually notice here are:

• ă = a short central vowel, similar to the a in sofa
• ț = ts, like in cats

So roughly:

• obosită ≈ o-bo-SEE-tuh
• că ≈ kuh
• dimineață ≈ dee-mee-NYEA-tsuh

These are only rough English approximations, but they help at the start.

Yes. Fiindcă also means because.

So you could say:

• Sunt obosită azi, fiindcă lucrez de dimineață.

Both are correct. In many situations they are interchangeable. Pentru că is extremely common and very neutral, so it is a great choice for learners.