L’addetto mi fa passare all’ingresso perché il biglietto è valido.

Because it is a shortened form of lo addetto.

In Italian, lo is the masculine singular definite article used before certain sounds, but before a vowel it usually becomes l’:

• lo addetto → l’addetto

So l’addetto means the staff member, the attendant, or the employee, depending on context.

Addetto means a person assigned to a particular job or function. In this sentence, l’addetto is probably:

• an attendant
• a staff member
• a gate employee
• someone checking entry

You will often see addetto in expressions like:

• addetto alla sicurezza = security staff member
• addetto alla reception = reception staff member
• addetto alle vendite = sales assistant

Mi means me and is an indirect object pronoun here.

In mi fa passare, it means makes/allows me to pass.

So the structure is:

• fa = he/she makes / lets
• mi = me
• passare = pass / go through / enter

Italian places object pronouns like mi, ti, gli, le, ci before the conjugated verb:

• mi fa passare = he/she lets me through

Because fare + infinitive is a very common Italian structure meaning to make someone do something or to let someone do something.

So:

• mi fa passare = he/she lets me pass / allows me through

This is different from:

• passo = I pass
• passa = he/she passes

Here, the attendant is not the one passing. The attendant is allowing me to pass.

This construction is extremely common:

• Mi fa entrare = He/She lets me enter
• Ci fa sedere = He/She makes us sit down
• Lo fanno uscire = They make him go out / let him out

In a sentence like this, the most natural English meaning is lets me pass or allows me through.

Literally, fare + infinitive can sometimes look like make someone do something, but in many real situations it means permission or allowing:

• L’addetto mi fa passare = The attendant lets me through

So context matters. Here, because we are dealing with an entrance and a valid ticket, lets me pass is the best interpretation.

All’ingresso is a contraction of:

• a + l’ingresso = all’ingresso

Here:

• a = at / to
• l’ingresso = the entrance

So all’ingresso means at the entrance or through the entrance, depending on context.

This kind of contraction is very common in Italian:

• a + il = al
• a + lo = allo
• a + la = alla
• a + l’ = all’
• a + i = ai
• a + gli = agli
• a + le = alle

Perché is the normal Italian word for because.

It can also mean why, depending on the sentence:

• Perché studi l’italiano? = Why are you studying Italian?
• Studio l’italiano perché mi piace. = I study Italian because I like it.

In your sentence, it clearly means because:

• perché il biglietto è valido = because the ticket is valid

Also note the accent: perché has an acute accent on the final é.

Yes, biglietto is a masculine singular noun, so it takes il in the singular:

• il biglietto = the ticket
• i biglietti = the tickets

In this sentence, il biglietto is the subject of the clause il biglietto è valido.

Here valido means valid.

So:

• il biglietto è valido = the ticket is valid

Be aware that valido can also mean good, capable, or worthy in other contexts, but with tickets, documents, and passes it usually means valid.

Examples:

• Il passaporto è valido. = The passport is valid.
• Questa carta non è più valida. = This card is no longer valid.

È is the third-person singular of essere (to be):

• io sono
• tu sei
• lui/lei è

So:

• il biglietto è valido = the ticket is valid

It agrees with il biglietto, which is singular.

Also, written Italian must include the accent on è. Without the accent, e means and.

The sentence is:

• L’addetto = subject
• mi fa passare all’ingresso = main verb phrase
• perché il biglietto è valido = reason clause

More literally:

• The attendant
• lets me pass at the entrance
• because the ticket is valid

So the overall structure is:

subject + object pronoun + fare + infinitive + place expression + perché-clause

Yes. Mi lascia passare is also very natural and often very close in meaning.

Compare:

• mi fa passare = lets me through / allows me through
• mi lascia passare = lets me through / allows me to pass

In many contexts, they are interchangeable. However:

• fare + infinitive is a very common causative structure
• lasciare + infinitive emphasizes permission a bit more directly

In this sentence, both work well.

Italian often expresses these ideas more compactly than English.

For example, English might say:

• lets me in
• lets me through
• lets me through the entrance

Italian can simply say:

• mi fa passare all’ingresso

The exact English translation depends on context, but the Italian is perfectly natural without needing extra words. Italian often relies on the verb passare plus the location phrase to convey the idea clearly.