Ce melon est plus sucré que la poire que j’ai mangée hier.

Because melon is a masculine singular noun in French.

French demonstratives agree with the noun:

• ce for masculine singular: ce melon
• cette for feminine singular: cette poire
• ces for plural: ces melons, ces poires

So ce melon is correct because melon is masculine.

It can mean either this melon or that melon. French ce/cet/cette/ces does not always make the same clear distinction that English makes between this and that.

Usually the context tells you which one is meant.

If French wants to make the contrast clearer, it can add:

• -ci = this one
• -là = that one

For example:

• ce melon-ci = this melon
• ce melon-là = that melon

Plus ... que is the standard way to make a comparison of superiority in French.

Here:

• plus = more
• sucré = sweet
• que = than

So plus sucré que means sweeter than or literally more sweet than.

The pattern is:

plus + adjective + que + noun/pronoun/clause

Examples:

• Ce melon est plus sucré que cette pomme.
• Paul est plus grand que Marie.

Related comparison patterns:

• moins ... que = less ... than
• aussi ... que = as ... as

Because adjectives usually agree with the noun they describe.

Here, sucré describes melon, which is:

• masculine
• singular

So the adjective stays in its masculine singular form: sucré

Compare:

• Ce melon est sucré.
• Cette poire est sucrée.

The feminine singular form adds an e: sucrée.

They do two different jobs.

1. The first que is part of the comparison:

   • plus sucré que la poire
   • sweeter than the pear

2. The second que is a relative pronoun:

   • la poire que j’ai mangée hier
   • the pear that I ate yesterday

So even though both are written que, they mean different things here:

• first que = than
• second que = that/which

Because French avoids putting je directly before a vowel sound.

When je comes before a verb beginning with a vowel or silent h, the e drops and becomes an apostrophe. This is called elision.

So:

• je ai becomes j’ai
• je aime becomes j’aime

That is why the sentence has j’ai mangée.

This is a very common learner question, because it involves an important agreement rule in the passé composé with avoir.

Normally, with avoir, the past participle does not agree:

• J’ai mangé la poire.

But if the direct object comes before the verb, the past participle agrees with that object.

Here:

• que stands for la poire
• la poire is feminine singular
• and it comes before ai mangée

So the participle agrees and becomes mangée.

Compare:

• J’ai mangé la poire. → no agreement, because the object comes after
• La poire que j’ai mangée → agreement, because the object comes before

French uses articles more often than English does, and here la poire refers to a specific pear.

The relative clause que j’ai mangée hier identifies which pear:

• the pear that I ate yesterday

So la is natural because this is a definite, identifiable pear.

If you said une poire, that would mean a pear, which is less specific.

Because in French, a relative clause like que j’ai mangée hier normally refers to the noun right before it.

So:

• la poire que j’ai mangée hier means
• the pear that I ate yesterday

The structure groups those words together as one unit.

If the speaker wanted to say that the melon was the thing eaten yesterday, the sentence would need to be structured differently.

Because that is a very natural position for a time expression in French, especially after a completed action.

In this sentence, hier belongs to j’ai mangée:

• the pear that I ate yesterday

Putting hier at the end sounds normal and clear.

French time expressions can sometimes move:

• Hier, j’ai mangé une poire.
• J’ai mangé une poire hier.

But in this sentence, final position is the most straightforward and idiomatic.

Usually, no. In normal pronunciation, mangé and mangée sound the same.

The extra e in mangée is mainly there to show written agreement with the feminine noun la poire.

So this is one of those cases where French spelling shows grammar that you often do not hear clearly in speech.