Learn Hardcore Italian: È importante che il bagaglio sia leggero per evitare costi extra. - It is important that the luggage be light to avoid extra costs.

che is the subordinating conjunction that links the impersonal main clause (È importante) to the subordinate clause. After impersonal expressions like È importante, Italian requires che to introduce the clause that follows.

Why is the verb sia (subjunctive) used instead of è (indicative) in the subordinate clause?

Expressions of importance, necessity, doubt, desire, and similar feelings (e.g. È importante che, È necessario che) trigger the subjunctive mood in Italian. Thus sia (subjunctive of essere) is mandatory; using è would be grammatically incorrect here.

Why is bagaglio singular and preceded by il?

In Italian, bagaglio can function like a mass noun—much like English luggage—to refer to the concept of baggage in general. When you speak of luggage generically, you typically use the singular with the definite article (il bagaglio), rather than a plural form.

Why is there no article before costi extra? Can we say per evitare dei costi extra?

When you mention costs in a general, unspecified sense, Italian often drops the article (zero article). Per evitare costi extra means “to avoid extra costs” in general. You could also use dei costi extra, which literally means “some extra costs,” but it’s less common in this kind of impersonal construction.

Why do we say per evitare costi extra instead of per evitare di costi extra?

After per indicating purpose (“in order to…”), Italian directly takes an infinitive verb (per evitare). You do not add di before costi extra. The di preposition would be used with certain verbs or adjectives, but not after per when expressing purpose.

What does costi extra mean, and why is extra placed after the noun costi?

costi is the plural of costo (“cost”), so costi extra translates to “extra costs” or “additional charges.” In Italian, descriptive adjectives normally follow the noun they modify, hence extra comes after costi.

Why doesn’t extra change form to agree with costi?

extra is an indeclinable adjective borrowed from English (originally Latin). In Italian it remains the same regardless of the noun’s gender or number, so you always say extra.

Could we place the adjective leggero before bagaglio, for example il leggero bagaglio?

While Italian does allow some adjectives to precede nouns for stylistic or poetic effect, most descriptive adjectives (like leggero) follow the noun in everyday usage. Il leggero bagaglio would sound unusual; il bagaglio leggero is the standard order.

Is it correct to rephrase the sentence using avere, like È importante avere un bagaglio leggero?

Yes. È importante avere un bagaglio leggero is a perfectly valid alternative. It avoids the subjunctive construction by using avere + noun and conveys the same idea about keeping your luggage light.