Instalu la enkursigilon, kondiĉe ke la elektringo funkcias.

Because instalu uses the -u ending, which marks a command, request, instruction, or exhortation in Esperanto.

• instalu = install / please install
• instalas = installs / is installing

So in this sentence, instalu is the correct form because the speaker is telling someone to do something.

In Esperanto, commands often leave the subject unspoken, just like English does in Install the router.

The understood subject is you. That could mean:

• one person
• more than one person
• a polite you

If you wanted to state it explicitly, you could say Vi instalu la enkursigilon, but usually that is unnecessary.

The -n marks the direct object.

Here, the thing being installed is la enkursigilo, so it becomes la enkursigilon.

A very literal breakdown is:

• instalu = perform the action of installing
• la enkursigilon = the thing receiving that action

This is one of the most important uses of -n in Esperanto.

Because la elektringo is the subject of funkcias, not the object.

In the clause la elektringo funkcias:

• la elektringo = the thing that functions
• funkcias = functions / is working

Subjects normally do not take -n. So the contrast is:

• la enkursigilon = object of instalu
• la elektringo = subject of funkcias

kondiĉe ke is a conjunction meaning something like provided that, on condition that, or as long as.

It introduces a condition for the main action.

So the structure is:

• main clause: Instalu la enkursigilon
• condition clause: kondiĉe ke la elektringo funkcias

A learner should treat kondiĉe ke as a set phrase.

Yes, in many contexts se could work, but the nuance is a little different.

• se = if
• kondiĉe ke = provided that / on condition that

kondiĉe ke sounds a bit more explicit and a bit more formal. It suggests that the condition must be satisfied before the action should happen.

So se is simpler, but kondiĉe ke is stronger and more precise here.

Because the clause is stating a condition as a normal fact or state, so the ordinary tense -as is used.

• funkcias = is working / works
• funkciu would suggest a wish, command, or volition, which is not the intended idea here

In other words, the sentence is not telling the electrical ring to work. It is saying that the installation should happen only if it is working.

la is Esperanto’s definite article, meaning the.

It is used here because the sentence seems to refer to specific things:

• la enkursigilon = the specific router
• la elektringo = the specific electrical ring/socket/circuit

Also, Esperanto has no separate indefinite article like a or an. So the contrast is simply:

• enkursigilo = router
• la enkursigilo = the router

Esperanto often builds technical vocabulary from smaller parts, and that makes long words more predictable than they may first appear.

A learner will often notice suffixes like:

• -il- = tool or device
• -o = noun ending
• -n = accusative ending

So enkursigilon is a noun for a device, and then -n is added because it is the direct object.

A useful general rule for Esperanto compounds is that the last main element is the core idea, and earlier parts modify it.

The comma is normal because kondiĉe ke la elektringo funkcias is a subordinate clause.

You can also reverse the order:

Kondiĉe ke la elektringo funkcias, instalu la enkursigilon.

That means the same thing. Esperanto word order is fairly flexible as long as the grammar is clear.

Not in this sentence.

When kondiĉe ke introduces a full clause, ke is part of the construction. So:

• correct: kondiĉe ke la elektringo funkcias
• not natural here: kondiĉe la elektringo funkcias

So it is best to learn kondiĉe ke as one unit.