La livella è sulla trave.

Because livella is a feminine singular noun, so it takes the feminine singular definite article la.

• la livella = the level
• il livello would be a different noun/form, not the one used here

In Italian, nouns normally need an article much more often than in English.

In Italian, nouns ending in -e can be either masculine or feminine. You usually have to learn the gender together with the noun.

So here:

• la trave = feminine
• singular article: la
• if needed, the plural is le travi

This is one of those cases where the ending alone does not tell you the gender.

Sulla means on the in this sentence.

It is a contraction of:

• su = on
• la = the (feminine singular)

So:

• su + la = sulla

This is very common in Italian. Prepositions often combine with articles.

Yes, in normal standard Italian, you use the contracted form sulla, not su la.

Just like:

• a + il = al
• di + la = della
• in + i = nei
• su + la = sulla

So La livella è sulla trave is the natural standard form.

The accent shows that è is the verb is from essere.

• è = is
• e without an accent = and

So the accent is important because it changes the meaning.

In this sentence:

• La livella è sulla trave = The level is on the beam
• without the accent, it would be incorrect here

Because this is a simple statement, and Italian often uses the same basic order as English:

• La livella = subject
• è = verb
• sulla trave = prepositional phrase

So the structure is:

subject + verb + place

Italian can be more flexible than English with word order, but this is the most neutral and natural order here.

Yes, you could. Sulla trave and sopra la trave are both possible, but they are not always felt exactly the same.

• sulla trave usually suggests direct contact: the level is resting on the beam
• sopra la trave can mean above/on top of the beam, sometimes with a slightly less direct sense of contact

In this context, if the object is physically resting on the beam, sulla trave is a very natural choice.

A simple English-friendly guide:

• livella ≈ lee-VEL-la
• trave ≈ TRAH-veh

A few details:

• In livella, the stress is on vel
• In trave, the stress is on the first syllable
• The Italian e in trave is pronounced clearly, not silent

And the whole sentence is roughly:

la lee-VEL-la eh SOOL-la TRAH-veh

Because Italian usually uses the article with nouns in cases like this where English might also use the.

So:

• sulla trave = on the beam

Leaving out the article would generally sound incomplete or unnatural in this sentence.

Yes, they are related in form, but they are not interchangeable.

• livella commonly means spirit level / bubble level
• livello often means level in more general senses, such as level, standard, height, degree

So in a sentence about a tool resting on a beam, livella is the right word.

Yes, Italian often drops the subject when it is clear from context.

So:

• La livella è sulla trave = full sentence, explicit subject
• È sulla trave = It is on the beam, with the subject understood

But if you are introducing the object for the first time or want to be clear, keeping La livella is better.