Pour comprendre un nouveau mot, vous n’avez qu’à comparer deux synonymes simples.

Pour + infinitive often means in order to ... or simply to ... when expressing purpose.

So pour comprendre un nouveau mot means to understand a new word or in order to understand a new word.

This is a very common French structure:

• pour apprendre = to learn / in order to learn
• pour réussir = to succeed / in order to succeed

The phrase pour comprendre un nouveau mot is an introductory purpose phrase. French often separates this kind of introductory element with a comma, especially in careful written style.

So the sentence is structured like this:

• Pour comprendre un nouveau mot, = introductory phrase
• vous n’avez qu’à comparer deux synonymes simples. = main clause

English does something similar:

• To understand a new word, you just have to compare two simple synonyms.

This is one of the most important parts of the sentence.

Ne ... avoir qu’à + infinitive means:

• to only have to
• to just have to
• all you have to do is ...

So vous n’avez qu’à comparer means:

• you only have to compare
• you just have to compare
• all you have to do is compare

Even though it contains ne ... que, it does not mean simple negation here.
It is a fixed pattern meaning only.

Compare:

• Vous n’avez qu’à attendre. = You just have to wait.
• Je n’ai qu’à appeler. = I only have to call.

Because the expression is avoir à + infinitive in this pattern.

Here is the structure:

• n’... que + à + infinitive

So:

• vous n’avez qu’à comparer literally works like:
• you have only to compare

The que becomes qu’ before à because of elision.

French avoids ne directly before a vowel sound. So ne becomes n’ before a word starting with a vowel or silent h.

Since avez begins with a vowel sound, you get:

• vous n’avez not
• vous ne avez

This is called elision.

You see the same thing in:

• je n’ai pas
• il n’est pas
• nous n’avons rien

Vous can mean:

1. you plural, or
2. you singular in a formal or general sense

In instructional or explanatory sentences, French often uses vous to address the reader politely or generally.

So here, vous is like English instructional you:

• To understand a new word, you just have to...

If you were speaking casually to one friend, you could say:

• Pour comprendre un nouveau mot, tu n’as qu’à comparer deux synonymes simples.

Both are possible, but they do not always mean exactly the same thing.

In many common cases, nouveau before the noun means new in the ordinary sense:

• un nouveau mot = a new word

When nouveau comes after the noun, it can sound more literary or can emphasize newly created, novel, or a contrast in meaning depending on context:

• un mot nouveau = a word that is new/novel

For everyday French, un nouveau mot is the normal choice.

This is part of a broader pattern: some common adjectives often come before the noun, including words like:

• petit
• grand
• jeune
• vieux
• nouveau
• bon
• mauvais

Most French adjectives come after the noun.
Simple is one of them in normal usage.

So:

• des synonymes simples = simple synonyms

This contrasts with adjectives like nouveau, which often come before the noun.

A useful rule of thumb:

• most adjectives go after the noun
• a smaller group of very common adjectives often go before

Here:

• synonymes = nouns
• simples = adjective describing them

Because of deux.

• deux synonymes = two synonyms
• the adjective must agree with the noun:
  • singular: simple
  • plural: simples

So:

• un synonyme simple
• deux synonymes simples

French adjectives usually agree in gender and number with the noun they describe.

Because the number word deux already determines the noun.

In French, cardinal numbers like un, deux, trois usually appear directly before the noun:

• deux livres
• trois personnes
• quatre idées

So:

• comparer deux synonymes simples not
• comparer les deux synonymes simples unless you mean two specific synonyms already known from context

Comparer is an infinitive, because it comes after à in the structure n’avoir qu’à + infinitive.

So:

• vous n’avez qu’à comparer

This is similar to English to compare, except French often uses the bare infinitive after another verb structure.

Comparer means to compare.
It is a regular -er verb:

• je compare
• nous comparons
• comparé
• comparer

In informal spoken French, speakers often drop the ne in ne ... que, although it is still present in careful writing.

Written / formal:

• Vous n’avez qu’à comparer deux synonymes simples.

Very common spoken form:

• Vous avez qu’à comparer deux synonymes simples.

However, learners should usually keep the full written form at first:

• vous n’avez qu’à

That is the standard form and the safest one to write.

Yes. French has several natural alternatives. For example:

• Pour comprendre un nouveau mot, il suffit de comparer deux synonymes simples.
  = To understand a new word, it is enough to compare two simple synonyms.

• Pour comprendre un nouveau mot, vous devez seulement comparer deux synonymes simples.
  = To understand a new word, you only need to compare two simple synonyms.

But vous n’avez qu’à is especially common when giving a simple instruction or reassuring someone that something is easy.

It often has the feeling of:

• just do this
• all you have to do is this