Σήμερα είμαι θυμωμένος, γιατί το λεωφορείο άργησε.

Greek often leaves out subject pronouns when they are clear from the verb form.
είμαι already means I am, so εγώ is not necessary.

You could say Εγώ είμαι θυμωμένος if you want extra emphasis, but in a neutral sentence it is usually omitted.

Σήμερα means today. It is an adverb of time, so it tells you when the speaker is angry.

It is placed at the beginning here because that sounds very natural, but Greek word order is flexible. You could also hear:

Είμαι θυμωμένος σήμερα, γιατί το λεωφορείο άργησε.

That still means the same thing.

είμαι is the 1st person singular of the verb είμαι = to be.

So:

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

In this sentence, είμαι θυμωμένος means I am angry.

θυμωμένος is the masculine singular form of the adjective/participle meaning angry. It agrees with the speaker.

If the speaker is female, you would say:

Σήμερα είμαι θυμωμένη, γιατί το λεωφορείο άργησε.

So the ending changes according to gender:

• θυμωμένος = masculine
• θυμωμένη = feminine
• θυμωμένο = neuter

Historically and grammatically, it behaves like a participle, but for many learners it is easiest to think of it as an adjective meaning angry.

It works the same way many Greek adjectives do: it changes for gender and number, and after είμαι it describes the subject.

So in practical terms, είμαι θυμωμένος is simply I am angry.

Yes, γιατί can mean both because and why.

In this sentence, it means because:

Σήμερα είμαι θυμωμένος, γιατί το λεωφορείο άργησε.
= Today I’m angry because the bus was late.

As a question word, it means why:

Γιατί είσαι θυμωμένος;
= Why are you angry?

So the meaning depends on context and punctuation.

The comma separates the main clause from the clause giving the reason:

• main clause: Σήμερα είμαι θυμωμένος
• reason clause: γιατί το λεωφορείο άργησε

In Greek, it is very common to use a comma before γιατί when it means because.

Here, το λεωφορείο is the subject of άργησε, so it is in the nominative.

λεωφορείο is a neuter noun, and in the singular the nominative and accusative forms are often the same:

• nominative: το λεωφορείο
• accusative: το λεωφορείο

So the form looks the same, but its role in the sentence tells you it is the subject.

The verb αργώ means to be late. So άργησε means was late or came late.

That means το λεωφορείο άργησε is a very natural Greek way to say:

• the bus was late
• the bus arrived late

It is not exactly the same as English delayed, although the meaning can overlap.

άργησε is the aorist, 3rd person singular, of αργώ.

In this sentence, the aorist presents the lateness as a completed event in the past: the bus was late on that occasion.

So:

• αργεί = it is late / it is being late
• άργησε = it was late / it came late

For this sentence, the aorist is the natural choice because the speaker is referring to a specific past event.

Yes. Το λεωφορείο καθυστέρησε also means the bus was delayed / the bus was late, and it is very natural Greek.

There is a slight difference in feel:

• άργησε focuses on being late
• καθυστέρησε focuses a bit more on being delayed

In everyday speech, both can work in a sentence like this.

Yes. Greek word order is more flexible than English word order.

The original sentence is very natural:

Σήμερα είμαι θυμωμένος, γιατί το λεωφορείο άργησε.

But you could also say:

Είμαι θυμωμένος σήμερα, γιατί το λεωφορείο άργησε.

or even:

Γιατί το λεωφορείο άργησε, σήμερα είμαι θυμωμένος.

That last version is less neutral and sounds more marked or emphatic. So the original is probably the best everyday choice.

A simple learner-friendly pronunciation guide is:

le-o-fo-REE-o

The stress is on -ρεί-.

One thing English speakers often notice is that Greek ει here sounds like ee, so the stressed part sounds like REE.

No. In this sentence, only the word agreeing with the speaker changes:

• male speaker: Σήμερα είμαι θυμωμένος
• female speaker: Σήμερα είμαι θυμωμένη

The rest of the sentence stays the same:

γιατί το λεωφορείο άργησε

No, but it is one of the most common and direct choices.

Another common word is νευριασμένος, which often feels more like annoyed, irritated, or worked up, though it can also mean angry depending on context.

So:

• θυμωμένος = angry
• νευριασμένος = annoyed / irritated / angry

For a straightforward sentence like this, θυμωμένος is an excellent choice.