No verão, eu uso tênis para caminhar, mas em casa prefiro chinelo.

Because no is a contraction of em + o:

• em = in
• o verão = the summer

So:

• em o verão → no verão

This is very common in Portuguese. Similar examples:

• no inverno = in the winter
• na primavera = in the spring
• no outono = in the fall

Yes, it can often be omitted.

Portuguese verbs usually show who the subject is, so uso already means I use/wear, and prefiro already means I prefer. Because of that, the sentence could also be:

• No verão, uso tênis para caminhar, mas em casa prefiro chinelo.

Including eu adds a little emphasis or clarity, but it is not required here.

Both are possible depending on context.

In this sentence, uso tênis is best understood as I wear sneakers/shoes. Portuguese often uses usar for wearing clothing, shoes, and accessories:

• usar tênis = to wear sneakers
• usar óculos = to wear glasses
• usar camisa = to wear a shirt

So even though usar literally looks like to use, it is also the normal verb for to wear in many contexts.

In Brazilian Portuguese, tênis can mean both:

• tennis (the sport)
• sneakers / tennis shoes

In this sentence, uso tênis clearly means I wear sneakers because of the context.

This is a very common word in Brazil for casual athletic shoes.

Grammatically, tênis has the same form in the singular and plural.

So:

• um tênis = one sneaker / one tennis shoe
• dois tênis = two sneakers / a pair of sneakers

In everyday use, usar tênis usually means to wear sneakers / tennis shoes in a general sense, even though the form does not change.

Portuguese often leaves out the article when talking about something in a general, category-like way.

So:

• prefiro chinelo = I prefer flip-flops/slippers
• prefiro o chinelo = I prefer the flip-flop / the slippers (more specific)

In this sentence, prefiro chinelo sounds natural because the speaker means footwear in general, not a specific pair.

Usually chinelo means flip-flop or sometimes slipper, depending on context.

In Brazil, chinelo very often refers to casual open footwear like Havaianas-type flip-flops. Since the sentence contrasts tênis for walking outside and chinelo at home, flip-flops/slippers is the idea.

Para caminhar means for walking or to walk and expresses purpose.

So:

• uso tênis para caminhar = I wear sneakers for walking

It tells you why the speaker wears sneakers.

Portuguese often uses para + infinitive to show purpose:

• Estudo para aprender. = I study to learn.
• Usei um casaco para sair. = I wore a coat to go out.

Em casa is a fixed, very common expression meaning at home.

• em casa = at home
• na casa = in/at the house

The second one usually refers to a specific house, often someone else’s house:

• Estou em casa. = I’m at home.
• Estou na casa da minha amiga. = I’m at my friend’s house.

So in this sentence, em casa is correct because it means at home in a general sense.

They are in the present indicative:

• uso = I use / I wear
• prefiro = I prefer

Here the present tense describes a habitual action or general preference, not necessarily something happening right now.

So the idea is:

• In summer, I generally wear sneakers for walking, but at home I generally prefer flip-flops.

It is very natural and helpful, though not always absolutely mandatory in every informal context.

No verão is an introductory time expression, and Portuguese often separates that with a comma:

• No verão, eu uso tênis...

This makes the sentence easier to read and sounds well-structured.

Yes, but the nuance is slightly different.

• no verão = in the summer
• durante o verão = during the summer

No verão is the more natural everyday choice here. Durante o verão sounds a bit more explicit or formal, but it is still correct.

Mas means but and introduces a contrast:

• uso tênis para caminhar = I wear sneakers for walking
• mas em casa prefiro chinelo = but at home I prefer flip-flops

It connects two contrasting habits or preferences.

Yes, a little. Portuguese allows some flexibility.

For example, these all sound natural:

• No verão, eu uso tênis para caminhar, mas em casa prefiro chinelo.
• No verão, uso tênis para caminhar, mas em casa prefiro chinelo.
• Eu uso tênis para caminhar no verão, mas em casa prefiro chinelo.

The original version is very natural because it starts with the time expression and then contrasts outdoor and home footwear clearly.

The original sentence is already natural. In casual speech, a Brazilian speaker might simply drop eu:

• No verão, uso tênis pra caminhar, mas em casa prefiro chinelo.

Notice that para often becomes pra in speech. That is extremely common and natural in Brazil.

So:

• para caminhar = more neutral/written
• pra caminhar = very common in spoken language