La capital está lejos.

Because capital changes meaning with the article:

• la capital = capital city
• el capital = capital, money, assets

So in this sentence, la capital is feminine because it means the capital city.

Spanish uses estar for location, and lejos describes where something is in relation to something else.

So:

• La capital está lejos. = the capital is far away.

Using ser here would sound wrong in normal Spanish. A good rule is:

• ser = what something is
• estar = where something is / how it is

Since this sentence is about location or distance, estar is the natural choice.

The accent mark shows both pronunciation and meaning.

• está = he/she/it is or you are (formal), from estar
• esta = this (feminine), as in esta ciudad

So the accent helps distinguish two different words. It also shows that the stress goes on the last syllable: es-TÁ.

Lejos is usually an adverb, meaning far or far away.

In this sentence, it works with estar to say that something is at a great distance:

• La capital está lejos.

Even though English often uses far almost like an adjective, in Spanish lejos is not normally treated like a regular adjective that changes form. It stays lejos.

Because the reference point is understood from the context.

• La capital está lejos. = The capital is far away.

If you want to say what it is far from, then you use de:

• La capital está lejos de aquí. = The capital is far from here.
• La capital está lejos de la costa. = The capital is far from the coast.

So:

• lejos = far away
• lejos de + place/person = far from ...

Normally, no.

In Spanish, singular count nouns usually need an article or some other determiner. So capital by itself would sound incomplete here.

Correct:

• La capital está lejos.

Spanish uses articles more often than English does, so where English may sometimes say capital, Spanish usually wants la capital.

A simple approximate pronunciation is:

lah cah-pee-TAHL es-TAH LEH-hos

A few notes:

• capital has stress on the last syllable: capi-TAL
• está has stress on the last syllable: es-TA
• j in Spanish sounds like a strong breathy h, so lejos sounds roughly like LEH-hos

The a vowels are short and clear, not like the many different a sounds in English.

Yes, but La capital está lejos is the most neutral and standard order.

You may sometimes hear other orders for emphasis, such as:

• Está lejos la capital.

That sounds more marked or stylistic. For most learners, the normal pattern to use is:

• subject + estar + lejos

So stick with La capital está lejos unless you have a reason to emphasize something.

Yes. Lejos is much more common in everyday speech.

• La capital está lejos. = very natural
• La capital está distante. = understandable, but more formal or less common in casual conversation

For normal conversation in Latin America, lejos is the better choice most of the time.

Most naturally, it refers to physical distance.

• La capital está lejos. = The capital is far away.

Because la capital is a place, listeners will usually understand this literally. In other contexts, lejos can be figurative, but here the basic interpretation is geographic distance.