Questa virgola non solo cambia il ritmo della frase, ma anche il suo significato.

Because virgola is a feminine singular noun in Italian, and the demonstrative adjective has to agree with it.

• questa virgola = this comma
• questo libro = this book

So:

• questa = feminine singular
• questo = masculine singular

The subject is questa virgola, which is singular: this comma.

So the verb must also be singular:

• questa virgola cambia = this comma changes
• If the subject were plural, you would use cambiano:
  • queste virgole cambiano = these commas change

It works very much like English not only ... but also ....

In this sentence:

• non solo cambia il ritmo della frase, ma anche il suo significato

means:

• it changes not only the rhythm of the sentence, but also its meaning

This structure is extremely common in Italian. It links two ideas and adds emphasis to the second one.

Other examples:

• Non solo è intelligente, ma anche simpatico.
• He is not only intelligent, but also nice.

Yes. That version is also correct, and many learners may find it easier to understand because non solo ... ma anche ... directly surrounds the two things being changed:

• non solo il ritmo della frase
• ma anche il suo significato

Both versions are natural. The original places emphasis a little earlier in the sentence, but the meaning is the same.

The comma helps separate the two parts of the contrastive structure:

• non solo ...
• ma anche ...

In writing, Italians often use a comma here, especially when the sentence is a bit longer. It makes the sentence easier to read and gives it a clearer rhythm.

So the comma is doing a real stylistic job here, which is fitting, since the sentence itself is talking about how a comma changes rhythm and meaning.

Della is a contraction of:

• di + la = della

So:

• il ritmo della frase literally means the rhythm of the sentence
• more literally still: the rhythm of the phrase/sentence

This is a very common Italian structure:

• il titolo del libro = the title of the book
• il colore della macchina = the color of the car

Italian uses definite articles much more often than English does.

Here:

• il ritmo della frase
• il suo significato

In English, we might say:

• the rhythm of the sentence
• its meaning

Italian usually keeps the article, even before a possessive:

• il suo significato = its meaning
• literally: the its meaning, though of course that is not how we translate it into English

This is normal Italian grammar.

Because Italian normally uses the definite article with possessive adjectives:

• il mio libro = my book
• la sua idea = his/her idea
• il suo significato = its meaning

The article is often omitted only in some family relationship expressions in the singular, such as:

• mia madre
• tuo fratello

But with ordinary nouns like significato, the article is normally required.

In this sentence, suo refers to la frase, not la virgola.

So:

• il suo significato = the sentence’s meaning / its meaning

The idea is that the comma changes:

1. the rhythm of the sentence
2. the meaning of the sentence

Even though virgola is the main subject of the sentence, the context makes it clear that suo belongs with frase.

Usually, yes, but not always perfectly.

In many contexts:

• frase = sentence

However, depending on context, frase can also mean:

• phrase
• expression
• statement

In this sentence, sentence is the most natural translation, because we are talking about punctuation, rhythm, and meaning in writing.

Anche adds the idea of also, completing the pattern not only ... but also ....

Compare:

• non solo ..., ma anche ... = not only ..., but also ...
• non solo ..., ma ... = possible in some contexts, but less complete and often less balanced

So anche makes the structure clearer and more idiomatic.

Sometimes yes, but its position can affect emphasis or sound less natural.

In this sentence, ma anche il suo significato is the most natural placement.

Italian word order with anche can be flexible, but it often sits right before the word or phrase it emphasizes. Here it emphasizes the second thing being changed:

• not only the rhythm
• but also the meaning

So the given position is a very good standard model for learners.

Yes: it is a nicely balanced, formal, explanatory sentence. It sounds like something you might read in a grammar explanation, writing guide, or language lesson.

A few features give it that tone:

• non solo ... ma anche ... creates a polished, balanced structure
• abstract nouns like ritmo and significato make it sound analytical
• the wording is precise and clear

So this is a useful sentence not only for grammar, but also as a model of formal written Italian.