C’è un apostrofo in quella frase, ma non c’è nessuna parentesi.

Because c’è is the shortened form of ci è.

In this expression, ci does not mean us. It is part of the fixed structure c’è / ci sono, which means there is / there are.

So:

• ci è → c’è
• c’è un apostrofo = there is an apostrophe

This apostrophe is an example of elision, where a vowel drops before another vowel.

C’è means there is.

Italian usually uses c’è and ci sono to express existence:

• C’è un libro sul tavolo. = There is a book on the table.
• Ci sono due libri sul tavolo. = There are two books on the table.

If you said just è, you would usually be saying is, not there is.

So:

• È un apostrofo would sound like It is an apostrophe
• C’è un apostrofo correctly means There is an apostrophe

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

This matters because Italian distinguishes:

• e = and
• è = is

So in c’è, the apostrophe and the accent do two different jobs:

• the apostrophe shows contraction of ci è
• the accent shows that è is the verb is

Because the two nouns have different grammatical gender.

• apostrofo is masculine singular
• parentesi is feminine singular

So the article or determiner must agree:

• un apostrofo
• nessuna parentesi

Agreement is very important in Italian. The word before the noun changes to match the noun’s gender and number.

Yes, apostrofo is masculine:

• un apostrofo
• l’apostrofo
• questo apostrofo

Its plural is usually apostrofi.

This matches the common pattern that nouns ending in -o are often masculine.

Because parentesi is a feminine noun, so you need the feminine form nessuna.

Compare:

• nessun libro = no book / not any book
• nessuna frase = no sentence / not any sentence
• nessuna parentesi = no parenthesis / not any parenthesis

So the form changes like this:

• nessun for many masculine nouns
• nessuna for feminine nouns

Here nessuna means no or not any.

So:

• non c’è nessuna parentesi = there is no parenthesis
• literally: there isn’t no parenthesis
• natural English: there isn’t any parenthesis / there is no parenthesis

Italian commonly uses double negation, where both non and nessuna appear together.

Yes, it is a double negative, and that is normal in Italian.

English standard grammar usually avoids this:

• English: There isn’t any parenthesis
• English: There is no parenthesis

But Italian commonly says:

• Non c’è nessuna parentesi

Here:

• non negates the verb
• nessuna reinforces the negative idea

This is standard Italian, not a mistake.

Because frase is feminine singular, so the demonstrative must also be feminine singular.

The forms are:

• quello for some masculine singular nouns
• quel / quello
• quella for feminine singular nouns
• quelli / quelle for plural

So:

• quella frase = that sentence
• quel libro = that book

Because when a preposition comes before a demonstrative like quella, you normally keep them separate:

• in quella frase
• con quella penna
• su quel tavolo

You do not combine in + quella into a single word.

By contrast, in + la becomes nella only when la is the article:

• nella frase = in the sentence
• in quella frase = in that sentence

So:

• nella frase = in the sentence
• in quella frase = in that sentence

Here it is singular.

This is a very common point of confusion because English has:

• parenthesis = singular
• parentheses = plural

Italian is different:

• la parentesi = singular
• le parentesi = plural

The noun parentesi keeps the same form in singular and plural. The article tells you which one it is.

So:

• nessuna parentesi = no parenthesis
• due parentesi = two parentheses

Yes. Alcuna can also mean any in a negative sentence, and it often sounds a bit more formal or written.

So these are both correct:

• non c’è nessuna parentesi
• non c’è alcuna parentesi

In everyday speech, nessuna is very common and natural.

Then you would usually switch from c’è to ci sono, because the noun becomes plural.

For example:

• Ci sono due apostrofi in quella frase.
• Non ci sono parentesi in quella frase.

So:

• c’è = there is
• ci sono = there are

That is one of the most important patterns in Italian.

It is pronounced roughly like cheh in English spelling, but with a clear Italian ch sound as in church, followed by an open e sound.

A rough guide:

• c’è ≈ cheh

Also remember that the stress falls on è.

So the start of the sentence:

• C’è un apostrofo...

sounds like:

• cheh oon apostrofo...

That is only an approximation, but it helps many learners.