La metgessa diu que aquest xarop curarà la tos.

Because metgessa is the feminine form of metge (doctor).

• el metge = the male doctor
• la metgessa = the female doctor

Catalan often marks gender in job titles and professions. Here the sentence is specifically talking about a female doctor, so it uses la metgessa.

Diu means says. It comes from the verb dir (to say / to tell).

This is the 3rd person singular present form:

• jo dic = I say
• tu dius = you say
• ell/ella diu = he/she says

So La metgessa diu... means The doctor says...

Que here means that and introduces a subordinate clause.

So:

• La metgessa diu = The doctor says
• que aquest xarop curarà la tos = that this syrup will cure the cough

Just like in English, that can sometimes be omitted in informal speech, but in Catalan que is very commonly used and sounds natural here.

Because xarop is a masculine singular noun.

The demonstratives must agree with the noun:

• aquest = this (masculine singular)
• aquesta = this (feminine singular)

So:

• aquest xarop = this syrup
• but aquesta medicina = this medicine

Xarop means syrup, especially medicinal syrup like cough syrup.

Yes, it is a normal and common word in Catalan. In this sentence, aquest xarop refers to this syrup.

A pronunciation point learners often notice: the x in xarop is usually pronounced like sh in English shoe.

Curarà is the future tense, 3rd person singular, from the verb curar (to cure).

So:

• curar = to cure
• curarà = he/she/it will cure

Here the subject is aquest xarop, so:

• aquest xarop curarà la tos = this syrup will cure the cough

The accent in curarà shows the stress: cu-ra-RÀ.

In Catalan, written accents often tell you which syllable is stressed and sometimes also distinguish forms. In the future tense, forms like curarà commonly have a written accent on the final syllable.

So the accent helps you pronounce it correctly.

La tos means the cough.

Catalan often uses the definite article with illnesses, symptoms, and body-related conditions in places where English may or may not use one. So la tos is completely natural.

Here it refers to the cough as the condition being treated.

Also, tos is a feminine noun, which is why it takes la.

Usually yes, but it is good to notice the pattern.

In this sentence:

• curar la tos = to cure the cough

Catalan can use curar with an illness, symptom, or person depending on context. In everyday use, it can overlap a bit with English cure or heal, but here will cure the cough is a very direct and natural translation.

Yes, it is very normal Catalan word order.

The structure is:

• La metgessa = subject
• diu = verb
• que... = subordinate clause

Inside the subordinate clause:

• aquest xarop = subject
• curarà = verb
• la tos = object

So it follows a very familiar pattern for English speakers: The doctor says that this syrup will cure the cough.

Yes, grammatically that is possible, because metgessa specifically means a female doctor.

But in natural English, you would usually just say The doctor says... unless the fact that the doctor is female matters in the context.

Catalan makes the gender explicit in the noun itself, while English usually does not.

A rough English-style pronunciation would be something like:

lah med-JESS-uh DEE-oo keh ah-KEST shah-ROP koo-rah-RAH lah toss

A few helpful notes:

• metgessa: the tg sound is not exactly like English, but med-JESS-uh is a useful approximation
• diu sounds roughly like DEE-oo
• aquest ends with a clear t
• xarop begins with sh
• curarà is stressed on the last syllable
• tos has an o closer to a pure vowel than the English word toss

Yes. That is also grammatical.

It changes the focus slightly:

• La metgessa diu que aquest xarop curarà la tos = neutral, straightforward reporting
• Aquest xarop curarà la tos, diu la metgessa = puts more emphasis on this syrup will cure the cough

So the original sentence is the most basic and standard way to say it, but Catalan does allow some flexibility in word order for emphasis.