Sans la virgule, la phrase est plus difficile à comprendre.

Sans means without.

In Sans la virgule, it introduces what is missing: without the comma.

A few similar examples:

• sans sucre = without sugar
• sans problème = without a problem / no problem
• sans toi = without you

So the first part of the sentence sets the condition: without the comma.

In French, singular countable nouns usually need an article such as le, la, or un/une.

So:

• la virgule = the comma
• la phrase = the sentence

English often drops articles in places where French keeps them, but French generally does not.

Here, la virgule refers to a specific comma being discussed, and la phrase refers to the sentence in question.

The comma separates the introductory phrase from the main clause.

Structure:

• Sans la virgule = introductory phrase
• la phrase est plus difficile à comprendre = main clause

In English, we often do the same:

• Without the comma, the sentence is harder to understand.

The comma helps readability, especially because the sentence is talking about a comma and its effect on meaning.

Because this is a comparison, not a negation.

In French, plus can mean:

• more
• or, in negative structures, no longer

Here there is no ne and the meaning is clearly comparative:

• plus difficile = more difficult

Compare:

• C’est plus simple. = It’s simpler / more simple.
• Ce n’est plus simple. = It is no longer simple.

So in this sentence, plus difficile definitely means more difficult.

This is a very common French structure:

• adjective + à + infinitive

So:

• difficile à comprendre = difficult to understand
• facile à lire = easy to read
• impossible à oublier = impossible to forget

It works much like English difficult to understand.

So:

• la phrase est plus difficile à comprendre
  literally: the sentence is more difficult to understand

Because it follows the pattern adjective + à + infinitive.

After difficile à, French uses the base verb form:

• à comprendre
• à lire
• à expliquer

It does not need to be conjugated, because it is not the main verb of the sentence.

The main conjugated verb is est:

• la phrase est...

Everything after that describes how the sentence is:

• plus difficile à comprendre

Yes. That version is completely natural.

Compare:

• Sans la virgule, la phrase est plus difficile à comprendre.
• La phrase est plus difficile à comprendre sans la virgule.

Both mean the same thing. The difference is mainly emphasis:

• Sans la virgule, ... puts the condition first.
• La phrase est plus difficile..., sans la virgule starts with the main point and adds the condition afterward.

French allows both word orders here.

Sometimes French does omit the article after sans, but not always.

Both patterns exist:

• sans article in some general expressions
• sans + article + noun when referring to something specific or when the noun normally needs it

Here, sans la virgule is the most natural choice because it refers to a particular comma in a particular sentence.

Sans virgule might sound more general, like talking about writing style or punctuation in general, rather than one specific comma.

The subject is la phrase.

Full structure:

• Sans la virgule = introductory prepositional phrase
• la phrase = subject
• est = verb
• plus difficile à comprendre = complement describing the subject

So the core sentence is:

• La phrase est plus difficile à comprendre.

And Sans la virgule adds the condition.

Here, plus is usually pronounced because it means more.

So in plus difficile, speakers normally pronounce the final s as a z sound before the vowel/d-sound beginning of the next word:

• roughly: pluz difficile

That helps distinguish it from some negative uses of plus, where the final sound may disappear:

• je ne veux plus = often pronounced more like plu

So in this sentence, learners should expect plus to be heard clearly as part of the comparison.