Sans apostrophe, cette phrase paraît moins naturelle à l’écrit.

After sans (without), French often uses a noun without an article when speaking in a general way.

So:

• sans apostrophe = without an apostrophe
• sans sucre = without sugar
• sans problème = without any problem / no problem

You can sometimes see an article after sans, but here the article-free version is the most natural.

Paraît is the third-person singular form of paraître, which usually means:

• to seem
• to appear

So cette phrase paraît moins naturelle means:

• this sentence seems less natural
• or this sentence appears less natural

It is a slightly more formal or polished verb than just saying semble in some contexts, though both can often work.

Because naturelle agrees with cette phrase, and phrase is a feminine singular noun.

So:

• un texte naturel = a natural text
• une phrase naturelle = a natural sentence

Since phrase is feminine, the adjective becomes naturelle.

À l’écrit means in writing or in written form.

It contrasts with à l’oral, which means in speech or when spoken.

So the sentence means that without the apostrophe, the phrase feels less natural when written, even if it might be understood anyway.

Examples:

• À l’écrit, c’est correct. = In writing, it is correct.
• À l’oral, on ne remarque pas la différence. = In speech, you don’t notice the difference.

Because écrit here is being used like a noun, and French needs the article le after à:

• à + le = au
• but before a vowel, le becomes l’

So:

• à le écrit → impossible
• à l’écrit = correct

This is the same kind of structure as:

• à l’école
• à l’intérieur
• à l’oral

That apostrophe comes from elision.

The article le becomes l’ before a word beginning with a vowel or silent h:

• le écrit → l’écrit
• le ami → l’ami
• le homme → l’homme

So l’écrit is just le écrit shortened in the normal French way.

Cette means this and is the feminine singular demonstrative adjective.

It agrees with phrase, which is feminine singular:

• ce livre = this book
• cet exercice = this exercise
• cette phrase = this sentence
• ces phrases = these sentences

So cette phrase simply means this sentence.

French often places a short introductory phrase at the beginning of the sentence, followed by a comma.

Here:

• Sans apostrophe = introductory phrase
• cette phrase paraît moins naturelle à l’écrit = main clause

This is very natural in French. It is similar to English:

• Without an apostrophe, this sentence seems less natural in writing.

You could also imagine other openings like:

• À l’oral, cette phrase passe mieux.
• Sans contexte, cette remarque paraît étrange.

The accent in paraît is a circumflex accent: î.

It is part of the standard spelling of the verb paraître in many forms:

• il paraît
• elle paraît
• paraître

You may sometimes notice spelling reform discussions around words with circumflex accents, but paraît is still a very normal spelling to know and recognize.

Not necessarily.

Moins naturelle means less natural, not automatically incorrect.

That suggests a difference between:

• something grammatically possible
• and something that sounds more idiomatic or more standard

So the idea is:

• without the apostrophe, the sentence may still be understood
• but it looks less natural in written French

That kind of comment is very common in language learning, because a form can be understandable without being the most natural one.

Yes, in many contexts you could say:

• Sans apostrophe, cette phrase semble moins naturelle à l’écrit.

That would also mean Without an apostrophe, this sentence seems less natural in writing.

The difference is small here:

• sembler = to seem
• paraître = to seem / appear

Both are common, but paraître can sound slightly more formal or stylistically polished depending on context.