sopa mite hyudaeponi tteoreojyeo isseoyo.

It is 떨어지다 + -아/어 있다.

• 떨어지다 = to fall
• 떨어져 있다 = to be in a fallen state / to have fallen and now be there
• 있어요 makes it polite and present-state

So this is not just describing the action of falling. It describes the resulting state: the phone has fallen and is now lying there.

This is a very common question.

• 떨어졌어요 = it fell
  • focuses more on the event
• 떨어져 있어요 = it is lying there after having fallen
  • focuses more on the current state

In this sentence, 떨어져 있어요 is natural because the speaker is describing where the phone is now, not mainly reporting the moment it fell.

Because 에 marks a location where something exists or is located.

Here, the phone is simply under the sofa. It is not doing an action there.

• 에 = at, in, on, to, under, etc. as a location marker for existence/destination
• 에서 = at/in a place where an action happens

Since 휴대폰이 ... 있어요 is about existence/location, 에 is correct.

이/가 is the subject marker, and here it helps present the phone as the thing being identified or noticed.

• 휴대폰이 떨어져 있어요 = the phone is lying there / it is the phone that is there
• 휴대폰은 떨어져 있어요 would sound more like setting up the phone as a topic, perhaps contrasting it with something else

In simple observations like this, 이/가 is very common.

밑 means the bottom, underside, or the area underneath something.

So:

• 소파 밑 = under the sofa
• 소파 밑에 = under the sofa + location marker

It works like a noun, which is why it needs a particle such as 에.

No. 소파 is a loanword from sofa.

Korean has many loanwords, especially for modern objects. The pronunciation is adapted to Korean sound patterns:

• sofa → 소파
• 휴대폰 is different: it is not a direct English loanword like 핸드폰; it is a Korean-made word meaning roughly portable phone

Because -아/어 있다 is a grammatical construction using the auxiliary verb 있다, and it is normally spaced separately.

So:

• 떨어져 = connected form of 떨어지다
• 있어요 = polite present form of 있다

Together, they mean is in the state of having fallen.

Not necessarily.

The verb here is 떨어지다, which is intransitive. It means to fall. It describes what happened to the phone, not who caused it.

If you want to say someone dropped the phone, Korean usually uses 떨어뜨리다, which is transitive:

• 휴대폰을 떨어뜨렸어요 = Someone dropped the phone

So 휴대폰이 떨어져 있어요 focuses on the phone’s current condition and location, not on the person who caused it.

Korean often leaves that kind of information unstated if it is clear from context.

So 휴대폰이 can mean:

• the phone
• a phone
• my phone
• the cellphone

depending on the situation.

Korean does not use articles like the and a. Possession is also often omitted when obvious. If needed, the speaker could say:

• 제 휴대폰이 = my phone
• 그 휴대폰이 = that phone

있어요 is the polite informal style, often called 해요체. It is very common in everyday speech.

Related forms:

• 있어 = casual
• 있어요 = polite everyday
• 있습니다 = formal polite

So 소파 밑에 휴대폰이 떨어져 있어요 is a natural, polite sentence for normal conversation.

Yes, Korean word order is flexible, though some orders sound more natural in context.

The original sentence:

• 소파 밑에 휴대폰이 떨어져 있어요

is very natural because it first gives the location, then introduces what is there.

You could also say:

• 휴대폰이 소파 밑에 떨어져 있어요

This is also correct. The difference is mostly about emphasis and flow, not basic meaning.