Alter puer dicit se e somno surgere nolle, quia somnus adhuc dulcis sit.

Alter originally means the other (of two), so if the story has already mentioned one boy, alter puer most naturally means the other boy.

In some contexts, it can also be understood more loosely as another or a second boy. But unlike alius, which is the ordinary word for another/different, alter often suggests a choice between two.

Se is the reflexive pronoun, and it refers back to the subject of dicit, namely alter puer.

So:

• alter puer dicit se ... nolle = the other boy says that he does not want ...

If Latin used eum, it would usually mean that he says that some other male person does not want ..., not himself.

This is a standard Latin indirect statement construction.

After a verb of saying, thinking, knowing, and so on, Latin often uses:

• an accusative subject
• plus an infinitive

So here:

• dicit = he says
• se = accusative subject of the indirect statement
• nolle = infinitive

Literally, Latin says something like:

• he says himself not to want ...

Natural English turns that into:

• he says that he does not want ...

Because they do two different jobs.

• nolle depends on dicit as part of the indirect statement.
• surgere depends on nolle and completes its meaning.

So the structure is:

• dicit → se nolle
• nolle → surgere

In English:

• he says that he does not want
• to get up

So surgere is the infinitive that goes with nolle.

Because nolo, nolle is the normal Latin verb meaning to be unwilling or not to want.

It is historically a contracted form of non volo, but in ordinary Latin it functions as its own common verb:

• nolo = I do not want
• non vis = you do not want
• non vult / nolo? Actually the standard forms are nolo, non vis, non vult, nolumus, non vultis, nolunt
• infinitive nolle

So here nolle is simply the usual infinitive form: not to want.

Somno is ablative singular.

That is because the preposition e (or ex) takes the ablative and means out of or from.

So:

• e somno = from sleep, out of sleep

With surgere, the phrase gives the sense to rise from sleep, that is, to wake up/get up from sleeping.

Literally, surgere means to rise, to get up, to stand up.

But in the phrase e somno surgere, it naturally means to rise from sleep, so in English we might translate it as:

• to get up
• to wake up
• to rise from bed

The exact English wording depends on context, but the Latin idea is the movement or act of coming out of sleep.

Because somnus is the subject of sit.

In the clause:

• quia somnus adhuc dulcis sit

the thing that is still sweet is sleep, so somnus must be nominative.

That is why the sentence is not using somnum here. Somnum would be accusative, which would not fit this clause.

Because dulcis agrees with somnus, which is masculine singular nominative.

Dulcis is a third-declension adjective. Its masculine and feminine nominative singular form is dulcis, while the neuter nominative singular is dulce.

So:

• somnus dulcis = sleep is sweet

If the noun were neuter, then dulce would be used instead.

This is one of the most important questions in the sentence.

Sit is subjunctive because the quia-clause is presenting the reason as part of the boy’s reported thought or claim, not necessarily as a fact independently asserted by the narrator.

So the sense is roughly:

• he says that he does not want to get up, because sleep is still sweet
• that is, this is his reason

In other words, the sweetness of sleep is being given from the boy’s point of view.

If Latin used est, that would sound more like the narrator is directly stating the reason as an objective fact:

• quia somnus adhuc dulcis est

No. Quia very often takes the indicative.

So learners should not think:

• quia = always subjunctive

That is not true.

Here the subjunctive appears because of the nuance of reported reason or because the reason is being presented as belonging to the speaker’s statement or thought. So this is a special use, not the default rule for quia.

Yes, the word order is flexible.

Latin uses endings more than position to show grammatical function, so the sentence could be rearranged in several ways without changing the basic meaning. For example, Latin could put nolle earlier or move e somno closer to surgere.

The given order is quite natural, though:

• alter puer sets up the subject
• dicit introduces the statement
• se e somno surgere nolle gives the indirect statement
• quia somnus adhuc dulcis sit adds the reason

So the order is not random, but it is not as rigid as English word order.

Only up to a point.

A very literal breakdown would be:

• alter puer = the other boy
• dicit = says
• se = himself
• e somno = from sleep
• surgere = to rise
• nolle = not to want

But natural English does not usually say he says himself not to want to rise from sleep. Instead we convert the Latin indirect statement into normal English:

• The other boy says that he does not want to get up from sleep / wake up

So a fully literal translation helps you see the grammar, but a natural translation is better English.