En invierno duermo mejor con un edredón grueso y una funda suave.

In Spanish, seasons are often used without the article after en when you mean during that season in a general sense.

• en invierno = in winter
• en verano = in summer

You can sometimes hear en el invierno, but it usually sounds more specific or stylistically heavier, like referring to a particular winter period or giving extra emphasis. In a normal general statement, en invierno is the most natural choice.

Spanish often drops subject pronouns because the verb ending already shows who is doing the action.

• duermo = I sleep
• duermes = you sleep
• duerme = he/she sleeps

So yo is not necessary unless you want to add contrast, emphasis, or clarity.

For example:

• En invierno duermo mejor. = normal, natural
• Yo duermo mejor, pero mi hermano no. = yo is used for contrast

Dormir is a stem-changing verb in the present tense. The o in the stem changes to ue in most forms.

Present tense of dormir:

• yo duermo
• tú duermes
• él/ella duerme
• nosotros dormimos
• vosotros dormís
• ellos/ellas duermen

So duermo is the correct yo form.

Because mejor is being used as an adverb here: it describes how the person sleeps.

• duermo mejor = I sleep better

You are not describing a noun; you are describing the verb duermo.

Compare:

• un buen edredón = a good duvet → adjective describing a noun
• duermo bien / duermo mejor = I sleep well / I sleep better → adverb describing a verb

Duermo mejor is the normal, neutral word order in Spanish: verb + adverb.

• duermo mejor = standard
• mejor duermo = possible only in special contexts, usually for emphasis or poetic/stylized wording

So for everyday Spanish, duermo mejor is what learners should use.

In Spain, edredón usually refers to a duvet or thick quilt/comforter used on the bed.

It is a masculine noun:

• un edredón
• el edredón

Related words:

• manta = blanket
• colcha = bedspread
• funda nórdica = duvet cover

Depending on context, English duvet, comforter, or quilt may overlap with edredón, but duvet is often the closest match in modern Spain Spanish.

Spanish adjectives usually come after the noun.

• un edredón grueso = a thick duvet
• una funda suave = a soft cover

Also, the adjective must agree with the noun in gender and number:

• edredón is masculine singular
• so the adjective is grueso

Compare:

• un edredón grueso
• una manta gruesa
• unos edredones gruesos
• unas mantas gruesas

Funda means cover or case. In bedding, it can refer to a cover for something on the bed. In context, it is understood as a bedding cover, often something like a duvet cover or another fabric cover.

It is a feminine noun:

• una funda
• la funda

In Spain, if you want to be very specific, you might also hear:

• funda nórdica = duvet cover
• funda de almohada = pillowcase

So una funda suave means a soft cover, and the exact type is understood from context.

Not all Spanish adjectives change their ending for gender.

Some adjectives have separate masculine and feminine forms:

• grueso / gruesa
• blanco / blanca

But others stay the same for both masculine and feminine:

• suave
• grande
• triste

So:

• un tejido suave
• una funda suave

Both are correct because suave does not change for gender.

Con means with. In this sentence, it expresses the thing that helps the speaker sleep better.

• duermo mejor con un edredón grueso = I sleep better with a thick duvet

It is similar to English with in many cases.

A few more examples:

• Trabajo mejor con música. = I work better with music.
• Estoy más cómodo con esta silla. = I’m more comfortable with this chair.

Because the sentence mentions two separate nouns, and each one needs its own article.

• un edredón grueso
• una funda suave

You cannot usually use one article for both if the nouns have different genders. Since edredón is masculine and funda is feminine, Spanish naturally uses:

• un ... y una ...

Usually yes, especially when the adjective gives a literal, descriptive quality, as in this sentence:

• edredón grueso
• funda suave

Putting the adjective before the noun is sometimes possible, but it can sound more literary, subjective, or emphatic, and sometimes the meaning changes.

For example:

• un edredón grueso = a duvet that is thick
• una suave funda = possible, but more stylistic than neutral everyday speech

For learners, the safest default is: noun + adjective

Edredón is pronounced roughly eh-dreh-DON.

The written accent mark shows that the stress falls on the last syllable:

• ed-re-dón

Without the accent mark, standard stress rules would suggest a different pronunciation. The accent is there to show the correct stress clearly.

This is common in Spanish:

• camión
• corazón
• edredón

All are stressed on the final syllable.