Minha irmã prefere iogurte sem açúcar, mas minha mãe gosta de biscoito com mel.

Because irmã and mãe are feminine nouns, and the possessive adjective has to agree with the thing possessed.

• meu = my, for masculine singular nouns
• minha = my, for feminine singular nouns
• meus = my, for masculine plural nouns
• minhas = my, for feminine plural nouns

So:

• minha irmã = my sister
• minha mãe = my mother

The verb gostar normally requires the preposition de before the thing that is liked.

• gostar de algo = to like something
• gostar de fazer algo = to like doing something

So:

• minha mãe gosta de biscoito com mel = my mother likes biscuits/cookies with honey

This is a very common point for English speakers, because English like does not need a preposition, but Portuguese gostar usually does.

Because preferir works differently from gostar.

• gostar de = to like
• preferir = to prefer

So you say:

• Ela gosta de iogurte.
• Ela prefere iogurte.

No preposition is needed before the noun after preferir in this sentence.

In Portuguese, as in English, foods are often used without an article when talking about them in a general sense.

So:

• prefere iogurte sem açúcar = prefers sugar-free yogurt / prefers yogurt without sugar
• gosta de biscoito com mel = likes biscuits/cookies with honey

You could sometimes hear articles in other contexts, but leaving them out here sounds natural and general.

• sem = without
• com = with

They are very common prepositions in Portuguese.

In this sentence:

• iogurte sem açúcar = yogurt without sugar
• biscoito com mel = biscuit/cookie with honey

This structure is very straightforward:

• noun + sem + noun
• noun + com + noun

Examples:

• café sem leite = coffee without milk
• chá com limão = tea with lemon

Mas means but.

It connects the two parts of the sentence:

• Minha irmã prefere iogurte sem açúcar
• mas minha mãe gosta de biscoito com mel

So it shows a contrast between the sister’s preference and the mother’s taste.

Accent marks in Portuguese help show pronunciation and stress, and sometimes they also distinguish spelling patterns that are not obvious to English speakers.

In this sentence:

• irmã: the ã shows a nasal sound
• mãe: the ãe is also nasal
• açúcar: the ç makes the c sound like s, and the acute accent in ú shows stress

A quick breakdown:

• ç = soft s sound, so açúcar sounds like assúcar, not akúcar
• ã / ãe = nasal vowels, very common in Portuguese

In Brazilian Portuguese, iogurte is usually pronounced roughly like yo-GOOR-chee or yo-GOOR-tee, depending on accent and speaking style.

A few notes:

• The i at the start sounds like y in yes
• The stress is on gur
• The final te in many Brazilian accents sounds close to chee or tee

A rough learner-friendly version is:

• iogurte ≈ yo-GOOR-chee

Not exactly in every context.

In Brazil, biscoito can refer to a range of things that English might call:

• biscuit
• cookie
• cracker

The exact meaning depends on region and context. In learning materials, biscoito is often translated as cookie or biscuit, but it is broader than either one.

So in this sentence, biscoito com mel could be understood generally as a biscuit/cookie with honey.

Because this is a simple, neutral Portuguese sentence, and Portuguese often uses a word order similar to English:

• subject + verb + object/complement

Here:

• Minha irmã = subject
• prefere = verb
• iogurte sem açúcar = object/complement

And:

• minha mãe = subject
• gosta de = verb phrase
• biscoito com mel = complement

So the sentence feels familiar to English speakers, even though some details, like gostar de, are different.

Yes, it could.

In Portuguese, possessives are sometimes used with a definite article:

• minha irmã
• a minha irmã

Both are possible, depending on region, style, and emphasis.

In Brazilian Portuguese, omitting the article before a possessive is very common and natural, especially in simple sentences like this one. So:

• Minha irmã prefere...
• Minha mãe gosta de...

sounds perfectly normal.

They express different kinds of preference.

• gostar de = to like
• preferir = to prefer

So:

• Minha irmã prefere iogurte sem açúcar means sugar-free yogurt is her preferred option
• Minha mãe gosta de biscoito com mel means she likes biscuits/cookies with honey, but it does not necessarily mean they are her favorite

So preferir is stronger and more comparative than gostar de.

Yes. In this sentence, both are being used as substances rather than countable items.

• açúcar = sugar
• mel = honey

That is why they appear without articles here:

• sem açúcar = without sugar
• com mel = with honey

This works very much like English. You are talking about the ingredient in general, not a specific sugar or a specific honey.