yeoreumeneun banpareul jaju ibeoyo.

Because the sentence is doing two things at once:

• 에 marks a time expression: in summer
• 는 makes that time expression the topic or adds a slight contrast: as for in summer...

So 여름에는 can feel like:

• In summer, ...
• When it comes to summer, ...
• At least in summer, ...

A very common shorter form is 여름엔.

Also, with seasons like 봄 / 여름 / 가을 / 겨울, Koreans often say just 여름에 or 여름에는, depending on nuance.

• 여름에 = neutral in summer
• 여름에는 = a bit more topic/contrast, like maybe compared with other seasons

Yes, absolutely.

• 여름에 반팔을 자주 입어요. = I often wear short sleeves in summer.
• 여름에는 반팔을 자주 입어요. = same basic meaning, but with a stronger topic/contrast feeling

For example, 여름에는 might sound especially natural if you are thinking about different seasons:

• 겨울에는 코트를 입고, 여름에는 반팔을 자주 입어요.
  In winter I wear a coat, and in summer I often wear short sleeves.

So both are correct. 에는 just adds a little emphasis.

반팔 literally means half sleeve, and in everyday Korean it usually means short sleeves or a short-sleeved top/shirt.

In this sentence, 반팔을 입다 means:

• to wear short sleeves
• to wear a short-sleeved shirt

Korean often uses this kind of shorthand naturally. You may also hear:

• 반팔 티셔츠 = short-sleeved T-shirt
• 반팔 옷 = short-sleeved clothes
• 반팔 셔츠 = short-sleeved shirt

But in casual everyday speech, just 반팔 is very common.

Because 입다 means to wear, and the thing being worn is the direct object.

So:

• 반팔 = short sleeves / a short-sleeved shirt
• 을 = object particle
• 입어요 = wear

So 반팔을 입어요 literally means wear short sleeves.

In casual speech, the object particle is often dropped:

• 여름에는 반팔 자주 입어요.

That sounds natural too, especially in conversation. But the full textbook form with 을 is clearer for learners.

자주 means often, and frequency adverbs in Korean usually come before the verb.

So the natural order is:

• 여름에는 반팔을 자주 입어요.

This is similar to English I often wear...

Korean word order is somewhat flexible, but 자주 usually appears near the verb it modifies. For example:

• 저는 커피를 자주 마셔요. = I often drink coffee.
• 주말에 영화를 자주 봐요. = I often watch movies on weekends.

If you move 자주 around, the sentence may still be understandable, but this placement is the most standard and natural.

입어요 is the present polite form of 입다 (to wear).

Breakdown:

• dictionary form: 입다
• verb stem: 입-
• polite ending: -어요
• result: 입어요

This is the very common polite everyday style, sometimes called 해요체.

It is appropriate in many normal situations:

• speaking politely to someone
• textbook examples
• daily conversation with people you are not close enough to use casual speech with

Related forms:

• 입어요 = polite present
• 입습니다 = more formal
• 입어 = casual/informal
• 입었어요 = wore / have worn
• 입을 거예요 = will wear

Here it most naturally means a habitual/general action, not something happening right this moment.

So the sentence means:

• I often wear short sleeves in summer
• not usually I am wearing short sleeves right now in summer

Korean present tense often covers:

• general facts
• habits
• repeated actions
• sometimes current actions, depending on context

Because of 자주 (often) and 여름에는 (in summer), the sentence clearly sounds habitual.

Yes, the subject is omitted.

That is very normal in Korean when the subject is obvious from context. English usually needs a subject like I, but Korean often leaves it out.

So this sentence could mean:

• I often wear short sleeves in summer
• We often wear short sleeves in summer
• People often wear short sleeves in summer

In many learning materials, it is usually understood as I unless context says otherwise.

If you want to make it explicit, you could say:

• 저는 여름에는 반팔을 자주 입어요.
  I often wear short sleeves in summer.

Korean nouns usually do not show singular vs. plural the way English does.

So 반팔 could refer to:

• a short-sleeved shirt
• short sleeves
• short-sleeved clothes in a general sense

The sentence is understood generically: I often wear short sleeves / short-sleeved tops in summer.

Korean usually does not need a plural marker unless it is important to emphasize plurality.

Yes. Korean uses different verbs depending on what you wear.

입다 is used for clothes worn on the body, such as:

• shirts
• pants
• coats
• dresses

So 반팔을 입어요 is correct.

Other common verbs include:

• 쓰다 = wear on the head
  
  • 모자를 써요. = I wear a hat.
• 신다 = wear on the feet
  
  • 신발을 신어요. = I wear shoes.
• 끼다 = wear on fingers/hands, or put on glasses
  
  • 반지를 껴요. = I wear a ring.
  • 안경을 껴요. = I wear glasses.
• 메다 / 매다 can be used for bags or ties, depending on the item

So learners often ask why not just use one word for wear. In Korean, the verb depends on the item.

Yes, very natural.

• 반팔을 자주 입어요. = a bit broader, I often wear short sleeves
• 반팔티를 자주 입어요. = more specifically I often wear short-sleeved T-shirts

Both are common. The best choice depends on how specific you want to be.

For example:

• 여름에는 반팔을 자주 입어요. = In summer, I often wear short sleeves.
• 여름에는 반팔티를 자주 입어요. = In summer, I often wear short-sleeved T-shirts.

So the original sentence is natural, and 반팔티 is just a more specific alternative.