La unua sceno estas enuiga.

La is the definite article, equivalent to the in English.

A useful Esperanto point: la is always la. It does not change for:

• singular vs. plural
• masculine vs. feminine
• subject vs. object

So you get:

• la sceno = the scene
• la scenoj = the scenes
• Mi vidas la scenon = I see the scene

In this sentence, la unua sceno means the first scene.

Because unu means one, while unua means first.

Esperanto distinguishes:

• unu = one
• unua = first

So:

• unu sceno = one scene
• la unua sceno = the first scene

Ordinal numbers in Esperanto are formed with -a:

• unua = first
• dua = second
• tria = third

Because they are both adjectives.

In Esperanto:

• nouns end in -o
• adjectives end in -a
• adverbs end in -e

So here:

• sceno = noun
• unua = adjective describing sceno
• enuiga = adjective describing sceno

Even though they appear in different parts of the sentence, both are adjectives, so both take -a.

The -o tells you that sceno is a noun.

That is one of the most important patterns in Esperanto:

• sceno = a noun, scene
• bela = an adjective, beautiful
• bele = an adverb, beautifully

Also, -o does not mean the noun is feminine. Esperanto nouns are not automatically masculine or feminine just because of their endings. Sceno is simply a noun.

Estas is the present-tense form of esti, meaning to be.

So:

• mi estas = I am
• vi estas = you are
• li estas = he is
• ili estas = they are

Unlike English, Esperanto verbs do not change depending on the subject. The ending tells you the tense:

• -as = present
• -is = past
• -os = future

So estas always means is/am/are in the present, depending on context.

Because there is no direct object here.

In La unua sceno estas enuiga:

• la unua sceno is the subject
• estas links the subject to a description
• enuiga is a predicate adjective, describing the subject

The accusative -n is mainly used for a direct object. But here, nobody is receiving an action. The sentence is just saying what the subject is like.

Compare:

• La unua sceno estas enuiga. = The first scene is boring.
• Mi spektas la unuan scenon. = I watch the first scene.

In the second sentence, scenon gets -n because it is the direct object.

Enuiga is an adjective meaning boring in the sense of causing boredom.

It is built from:

• enui = to be bored
• -ig- = to cause, make
• -a = adjective ending

So enuiga literally means something like boredom-causing.

That is why it describes the scene, not the viewer. The scene causes boredom.

A useful contrast:

• Mi enuas. = I am bored.
• La sceno estas enuiga. = The scene is boring.
• La sceno enuigas min. = The scene bores me.

Because they do two different jobs.

• unua is directly attached to the noun sceno
• enuiga comes after estas because it is part of the predicate, describing the subject through the verb to be

So the structure is:

• La unua sceno = noun phrase
• estas enuiga = is boring

This is similar to English:

• the first scene
• is boring

Yes. Adjectives agree with the nouns they describe in number and case.

That means if the noun becomes plural or accusative, the adjective changes too.

Examples:

• la unua sceno = the first scene
• la unuaj scenoj = the first scenes
• Mi vidas la unuan scenon = I see the first scene
• Mi vidas la unuajn scenojn = I see the first scenes

In your sentence, everything is singular and not accusative, so the adjectives stay as:

• unua
• enuiga

To some extent, yes, because Esperanto word order is fairly flexible. But La unua sceno estas enuiga is the most neutral, natural order.

You might also see something like:

• Enuiga estas la unua sceno.

That puts extra emphasis on enuiga.

Still, for learners, the best default pattern is:

• article + adjective + noun
• subject + estas
  • adjective

So this sentence is a very standard model to follow.

Yes—an English speaker might want to pronounce it like English scene, but Esperanto spelling is much more regular.

In Esperanto:

• c is always pronounced ts
• s is always s

So sceno is pronounced roughly STSE-no.

A few more pronunciation notes for the whole sentence:

• La = lah
• unua = u-NU-a
• sceno = STSE-no
• estas = ES-tas
• enuiga = e-nu-I-ga

And the stress in Esperanto normally falls on the second-to-last syllable.