Los puños de mi jersey están mojados porque lavé la taza.

That’s a very common question. Puño can mean fist, but in clothing it also means cuff: the end part of a sleeve around the wrist.

So in Los puños de mi jersey, puños means the cuffs of my jumper/sweater, not my fists.

For example:

• Me duelen los puños = My fists hurt
• Los puños de la camisa están sucios = The cuffs of the shirt are dirty

In Spanish, especially in Spain, jersey usually means sweater or jumper, not a sports jersey.

So:

• un jersey = a sweater / jumper in Spain

This is a regional vocabulary point. In other Spanish-speaking countries, people might more often say:

• suéter
• sweater
• pulóver

But in Spain, jersey is very normal.

Because puño is a masculine noun.

• singular: el puño
• plural: los puños

Even though the thing being described is part of clothing, the gender depends on the noun itself, not on the object it belongs to.

Because mis puños would usually mean my fists, not the cuffs of my sweater.

The phrase los puños de mi jersey clearly tells you that we are talking about the cuffs belonging to my sweater.

So:

• mis puños = usually my fists
• los puños de mi jersey = the cuffs of my sweater

This is one reason the full phrase is helpful and natural.

Spanish uses estar for states or conditions that are seen as temporary, and ser for more permanent characteristics or definitions.

Here, being wet is a temporary condition, so Spanish uses estar:

• Los puños están mojados = The cuffs are wet

Using ser mojados would sound wrong here.

A useful comparison:

• La puerta está abierta = The door is open
• La puerta es blanca = The door is white

Open is a state; white is a characteristic.

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

The noun here is los puños:

• masculine
• plural

So the adjective must also be masculine plural:

• mojados

Agreement pattern:

• el puño mojado
• los puños mojados
• la manga mojada
• las mangas mojadas

Lavé is the preterite (also called the simple past) of lavar.

Conjugation:

• yo lavé = I washed
• tú lavaste = you washed
• él/ella lavó = he/she washed

It is used for a completed action in the past:

• lavé la taza = I washed the cup

The accent is important because it distinguishes the past tense from other forms.

• lavé = I washed
• lave = present subjunctive or formal command form, depending on context

So the written accent helps show that lavé is the yo form of the preterite.

Because porque (one word, no written accent) means because.

Here it introduces the reason:

• están mojados porque lavé la taza = they are wet because I washed the cup

Compare:

• porque = because
• por qué = why
• el porqué = the reason
• por que = a less common combination in specific structures

So in this sentence, porque is exactly the right form.

Spanish often uses the definite article when the object is specific or understood from the context.

So lavé la taza suggests:

• a particular cup
• the cup we already know about
• the cup involved in the situation

If you said lavé una taza, it would mean I washed a cup, with less emphasis on it being a specific one.

Both are grammatically possible, but they do not suggest exactly the same thing.

Not if you want the same meaning.

• las mangas = the sleeves
• los puños = the cuffs

The puños are just the ends of the sleeves, near the wrists. If only that part got wet, puños is more precise.

So:

• Las mangas están mojadas = the sleeves are wet
• Los puños están mojados = the cuffs are wet

Yes, it is completely normal.

The basic structure is:

• Los puños de mi jersey = subject
• están mojados = verb + adjective
• porque lavé la taza = reason clause

So the sentence follows a very standard order: subject + verb + description + reason

Spanish can sometimes move things around for emphasis, but this version is neutral and natural.

Yes. In Spain, both can be possible, depending on nuance and context.

• lavé la taza = simple completed past action
• he lavado la taza = present perfect; often used in Spain for a recent past action connected to the present

Since the wet cuffs are still relevant now, many speakers in Spain might also naturally say:

• Los puños de mi jersey están mojados porque he lavado la taza

So the original sentence is correct, but the present perfect could also sound natural in Peninsular Spanish.