Scusa, sono in ritardo.

Here, scusa means sorry or excuse me.

It comes from the verb scusare = to excuse. In this sentence, scusa is the informal singular imperative, so it is literally something like excuse me when speaking to one person you address with tu.

So Scusa, sono in ritardo is a very natural way to say Sorry, I’m late.

Both are possible.

• Scusa = sorry / excuse me
• Scusami = forgive me / excuse me with mi = me

Scusami can sound a little more explicit or slightly more personal, but in everyday speech both are common:

• Scusa, sono in ritardo.
• Scusami, sono in ritardo.

Both are natural in informal situations.

Scusa is informal. You use it with:

• friends
• family
• classmates
• people your age in casual situations

If you want to be formal, use:

• Scusi, sono in ritardo.

That is the polite form used with Lei.

In Italian, essere is the normal verb here, not stare.

• sono = I am
• in ritardo = late

So Italian says I am in lateness / I am late with essere:

• Sono in ritardo.

Using stare here would sound unnatural in standard Italian.

Literally, in ritardo means in delay or behind schedule.

It is a fixed expression in Italian:

• essere in ritardo = to be late

So even though English just says late, Italian usually uses this longer phrase.

No. Those would be wrong here.

To say I’m late, the normal expression is:

• Sono in ritardo.

Be careful because tardi usually means late as an adverb, as in:

• È tardi. = It’s late.
• Arrivo tardi. = I arrive late / I’m arriving late.

So:

• Sono in ritardo. = I’m late.
• Arrivo tardi. = I arrive late / I’m arriving late.

Italian often drops subject pronouns when they are not needed.

• (Io) sono in ritardo.

The verb sono already tells you the subject is I, so io is usually omitted.

You can include io for emphasis, contrast, or clarity:

• Io sono in ritardo, non tu. = I’m late, not you.

But in a normal sentence, just sono in ritardo is the most natural choice.

Yes. It is completely natural as it is.

It has:

• an apology: Scusa
• the explanation: sono in ritardo

In real conversation, Italians often use short sentences like this.

The comma separates the apology from the main statement:

• Scusa, sono in ritardo.

It works like English:

• Sorry, I’m late.

In casual texting, people may leave out punctuation, but with standard writing the comma is normal.

A simple guide is:

• Scusa → SKOO-zah
• sono → SOH-noh
• in ritardo → een ree-TAR-doh

A few helpful points:

• sc before u sounds like sk
• the stress in ritardo falls on tar
• Italian vowels are usually clear and pure, not reduced as much as in English

Yes, but the tone is a little different.

• Scusa, sono in ritardo. = direct, everyday, natural
• Mi dispiace, sono in ritardo. = I’m sorry, I’m late, often a bit more heartfelt or polite

Both work. Scusa is especially common in casual speech.

A few common alternatives are:

• Scusami, sono in ritardo.
• Scusi, sono in ritardo. formal
• Mi dispiace, sono in ritardo.
• Perdonami, sono in ritardo. stronger or more emotional
• Scusa il ritardo. = Sorry for the delay / Sorry I’m late

They are similar, but Scusa, sono in ritardo is one of the most basic and useful everyday versions.

Yes. Ritardo is a common noun meaning delay or lateness.

Examples:

• Il treno è in ritardo. = The train is late.
• C’è un ritardo di dieci minuti. = There is a ten-minute delay.
• Siamo in ritardo. = We’re late.

So learning in ritardo is very useful beyond this one sentence.