Metto la calcolatrice nello zaino.

Because Italian often drops the subject pronoun when it is already clear from the verb form.

• Metto = I put
• The ending -o shows that the subject is I

So Metto la calcolatrice nello zaino is a complete sentence by itself.

You could say Io metto la calcolatrice nello zaino, but that usually adds emphasis, as in:

• Io metto la calcolatrice nello zaino, non tu.
  I’m putting the calculator in the backpack, not you.

Metto is the first person singular present tense of mettere, which means to put or to place.

Present tense of mettere:

• io metto = I put
• tu metti = you put
• lui/lei mette = he/she puts
• noi mettiamo = we put
• voi mettete = you all put
• loro mettono = they put

So here, metto means I put or I am putting, depending on context.

Italian uses articles very often, more often than English learners sometimes expect.

Here:

• la = the
• calcolatrice = calculator

So la calcolatrice means the calculator.

In a sentence like this, using the article is the normal choice when talking about a specific object. Leaving it out would usually sound incomplete or unnatural in standard Italian.

Also, calcolatrice is a feminine singular noun, so it takes la.

You usually learn the gender together with the noun:

• la calcolatrice = the calculator

Many nouns ending in -trice are feminine, so that is a useful pattern. But the safest habit is to memorize nouns with their article:

• la calcolatrice
• lo zaino

That way, you learn both the word and its gender at the same time.

Nello is a combination of:

• in = in, into
• lo = the

So:

• in + lo = nello

This is called a contracted preposition.

Therefore:

• nello zaino = in the backpack / into the backpack

Because zaino begins with z, and in Italian, masculine singular nouns beginning with certain sounds take lo, not il.

You use lo before nouns beginning with:

• z → lo zaino
• s + consonant → lo studente
• ps → lo psicologo
• gn → lo gnomo
• x, y in many cases

Since zaino starts with z, the correct article is:

• lo zaino

And after in, that becomes:

• nello zaino

Because the article for zaino is lo, not il.

Compare:

• in + il = nel
• in + lo = nello

So:

• nel libro = in the book
• nello zaino = in the backpack

Since zaino takes lo, the sentence must use nello.

In this sentence, it is best understood as into the backpack, because the verb mettere expresses movement or placement.

• Metto la calcolatrice nello zaino = I put the calculator into the backpack.

But in many cases, Italian uses in + article where English might choose either in or into. The exact meaning depends on the verb and context.

So with mettere, the idea of movement into something is natural.

This is a very normal Italian word order:

• Metto = verb
• la calcolatrice = direct object
• nello zaino = place/destination

So the structure is basically:

verb + object + place

This matches English quite closely:

• I put + the calculator + in/into the backpack

Italian word order can be flexible, but this version is the most neutral and natural.

Yes, you could. Italian allows some flexibility in word order.

• Metto la calcolatrice nello zaino = neutral, standard
• Metto nello zaino la calcolatrice = still correct, but it may place a little more focus on where you are putting it

So both are possible, but the original sentence is the most straightforward one for everyday use.

It can mean both.

Italian simple present often covers both:

• I put
• I am putting

So:

• Metto la calcolatrice nello zaino can mean
  • I put the calculator in the backpack
  • I’m putting the calculator in the backpack

Context tells you which meaning is intended.

Yes, but it is slightly different in feel.

• nello zaino = in the backpack / into the backpack
• dentro lo zaino = inside the backpack

Dentro adds a stronger sense of inside.
In this sentence, nello zaino is the most natural everyday phrasing.

Also note:

• dentro lo zaino does not contract the same way as in + lo
• so it stays dentro lo zaino, not dentronello or anything like that

Yes.

In this sentence:

• metto = the action
• la calcolatrice = the thing being put
• nello zaino = where it is being put

So la calcolatrice is the direct object.

This matters because if you later replace it with a pronoun, you would use a direct object pronoun:

• La metto nello zaino.
• I put it in the backpack.

Here, la means it, referring to la calcolatrice.

Yes, zaino usually means backpack or rucksack.

Examples:

• lo zaino di scuola = school backpack
• mettere qualcosa nello zaino = put something in the backpack

It is a very common everyday word.

A simple pronunciation guide is:

MEHT-toh la kal-koh-lah-TREE-che NEHL-loh DZAI-noh

A few useful points:

• tt in metto is pronounced clearly as a double consonant
• ci in calcolatrice sounds like chee
• z in zaino is pronounced like dz in many standard pronunciations

You do not need perfect pronunciation right away, but it helps to notice:

• metto has a strong double t
• nello has a double l