Sono lieto di aiutare.

Sono is the first-person singular form of essere (to be), so it means I am.

So Sono lieto di aiutare literally means something like I am pleased to help or I am glad to help.

Italian often leaves out subject pronouns when they are not needed, because the verb ending already shows who is doing the action.

In sono, the ending tells you it means I am, so io is usually unnecessary.

You could say Io sono lieto di aiutare, but that would normally add emphasis, like I am glad to help.

Lieto means glad, pleased, or happy in a somewhat polite or formal way.

In everyday speech, many Italians might more often say:

• Sono felice di aiutare
• Sono contento di aiutare

Compared with those, lieto can sound a bit more elegant, courteous, or formal. It is very natural in polite service language, writing, and formal conversation.

Lieto is the masculine singular form.

If the speaker is male, they say:

• Sono lieto di aiutare

If the speaker is female, they usually say:

• Sono lieta di aiutare

This is because many Italian adjectives agree in gender and number with the person they describe.

After adjectives like lieto, Italian often uses di + infinitive to express what someone is glad, happy, sorry, ready, etc. to do.

So:

• lieto di aiutare = glad to help

This pattern is very common:

• Sono felice di vederti = I’m happy to see you
• Sono pronto a partire = I’m ready to leave
  (Notice that some adjectives use a, not di, so the preposition depends on the expression.)

Aiutare is the plain infinitive to help.

In Sono lieto di aiutare, the sentence is general: I am glad to help.

If you want to specify whom you are helping, Italian can attach a pronoun to the infinitive:

• aiutarti = to help you (informal singular)
• aiutarla = to help you (formal) or to help her
• aiutarvi = to help you (plural)
• aiutarlo = to help him

So you may also hear:

• Sono lieto di aiutarla = I’m glad to help you (formal)

It sounds polite and somewhat formal, mainly because of lieto.

It is very appropriate in customer service, business communication, polite replies, or formal writing.

In more casual everyday speech, someone might say:

• Sono felice di aiutarti
• Sono contento di aiutarti
• Mi fa piacere aiutarti

All are natural, but Sono lieto di aiutare has a more courteous tone.

Yes, it can absolutely be used on its own.

It works as a general statement meaning I’m glad to help. The listener understands the object from context.

But you can also make it more specific:

• Sono lieto di aiutarti
• Sono lieto di aiutarla
• Sono lieto di aiutare la tua famiglia

So the shorter version is perfectly natural when the situation already makes the meaning clear.

Yes. The full sentence Sono lieto di aiutare includes the verb sono and is a complete sentence: I am glad to help.

Lieto di aiutarla leaves out sono and is more like a shortened polite expression, especially in formal speech or writing. It can feel a bit like:

• Glad to help you
• Pleased to help you

Italian often allows this kind of shortening in polite formulas.

Aiutare is pronounced approximately ah-yoo-TAH-reh.

A learner may find aiu unusual at first. Try thinking of it in parts:

• a
• iu
• ta
• re

The stress falls on ta: aiuTÀre.

And the whole sentence is roughly:

• SO-no LYE-to dee ah-yoo-TAH-reh

The exact sound of lieto is not like English lee-eh-toh said slowly; the ie forms a smooth Italian vowel sequence. But for a beginner, that rough guide is good enough to start.

Not in natural English.

Although di aiutare literally corresponds to to help, the natural English translation is:

• I’m glad to help
• I’m pleased to help

So it is better to learn the whole pattern as:

• essere lieto di + infinitive
• to be glad/pleased to + verb

That will help you avoid overly literal translations.