Pladsen ved vinduet er ledig.

Because pladsen is the definite form of plads, meaning the seat / the place / the spot.

In Danish, the definite article is usually added to the end of the noun:

• en plads = a seat / a place
• pladsen = the seat / the place

So Pladsen ved vinduet er ledig means The seat by the window is available / free.

For the same reason: vinduet is the definite form of vindue, meaning the window.

• et vindue = a window
• vinduet = the window

So ved vinduet means by the window or at the window.

Because Danish nouns belong to different grammatical genders.

• plads is a common gender noun, so it takes:
  • en plads
  • pladsen
• vindue is a neuter noun, so it takes:
  • et vindue
  • vinduet

This is very common in Danish:

• common gender definite singular: -en
• neuter definite singular: -et

Ved usually means by, at, or near, depending on context.

In this sentence, ved vinduet means something like:

• by the window
• next to the window
• at the window

So it tells you the location of the seat.

Because Danish usually puts the at the end of the noun instead of using a separate word before it.

Compare English and Danish:

• the seat → pladsen
• the window → vinduet

This is one of the biggest structural differences from English.

However, Danish can also use a separate definite word in some cases, especially with adjectives:

• den ledige plads = the available seat

But in your sentence, there is no adjective directly attached to plads, so the ending alone is enough: pladsen.

Ledig means free, available, vacant, or unoccupied, depending on context.

In this sentence, ledig means that the seat is not taken.

Common uses:

• Pladsen er ledig = The seat is free
• Stolen er ledig = The chair is free
• Han er arbejdsløs/ledig can also mean he is unemployed, depending on context

So the basic idea is not occupied / available.

Because ledig is agreeing with pladsen, and plads is a common gender noun.

Danish adjectives often change form depending on the noun:

• common gender singular: ledig
• neuter singular: ledigt
• plural / definite contexts: ledige

Examples:

• En plads er ledig = A seat is free
• Et værelse er ledigt = A room is free
• Pladserne er ledige = The seats are free

So pladsen er ledig is correct because plads is common gender.

Yes. That would also be correct, but it is slightly more specific.

• plads = place / spot / seat
• sæde = seat, more literally

So:

• Pladsen ved vinduet er ledig can mean the place/seat by the window is free
• Sædet ved vinduet er ledigt means more specifically the seat by the window is free

Also note the adjective change:

• sæde is neuter: et sæde
• so you get ledigt, not ledig

That whole phrase is the subject: The seat by the window.

The sentence structure is very straightforward:

• Pladsen ved vinduet = subject
• er = verb
• ledig = subject complement / adjective

So the pattern is basically:

The seat by the window + is + free

This is normal Danish word order in a simple statement.

Yes, and that is also very natural Danish.

The two sentences are close in meaning, but the emphasis is different:

• Pladsen ved vinduet er ledig
  Focuses on that specific seat by the window

• Der er en ledig plads ved vinduet
  Means There is a free seat by the window
  Focuses on the existence of such a seat

So the first is more definite and specific, while the second introduces it as new information.

No. Plads is a flexible word.

It can mean:

• a seat
• a space
• a place
• room

Examples:

• Der er ikke plads = There is no room
• Har du plads? = Do you have space?
• en ledig plads = an available seat / spot

In your sentence, because of ved vinduet, it most naturally means seat or spot.

A careful pronunciation would be approximately:

PLADS-en veh VIN-doo-et er LEH-thi

A few helpful notes:

• pladsen: the d is not pronounced like a strong English d
• ved: often sounds softer than English learners expect
• vinduet: the ending can sound reduced in normal speech
• ledig: the g at the end is usually soft, not a hard English g

In natural spoken Danish, words are often reduced, so it may sound smoother and less clearly separated than the spelling suggests.

No. In modern Danish, nouns are not capitalized unless they begin the sentence or are part of a proper name.

So you write:

• Pladsen ved vinduet er ledig.

not with capitals on every noun.

That matches English more than German.

You would need plural forms for both the noun and the adjective.

For example:

• Pladserne ved vinduet er ledige = The seats by the window are free

Breakdown:

• pladser = seats
• pladserne = the seats
• ledige = free, plural/definite form

So the adjective changes too.

Yes, but the meaning depends on context.

For things like seats, rooms, tables, or spaces, ledig means:

• free
• vacant
• available

For people, especially in job-related contexts, ledig can mean:

• unemployed
• without a job

So context matters a lot. In your sentence, because it is about pladsen ved vinduet, it clearly means available / unoccupied.