Vi nepre devas veni.

Nepre adds extra force. It means something like definitely, absolutely, without fail, or by all means.

So:

• Vi devas veni = You must come
• Vi nepre devas veni = You absolutely must come / You must definitely come

It strengthens the obligation or urgency.

Vi can mean both:

• you (singular)
• you (plural)

Esperanto normally uses the same form for both, unlike some languages that distinguish them. The context tells you whether one person or more than one person is meant.

After a modal-like verb such as devi (to have to / must), the next verb stays in the infinitive form, which in Esperanto ends in -i.

So:

• devas = must / have to
• veni = to come

Together: devas veni = must come

You do not use the finite form venas here, because venas means comes / is coming, and only one verb in the clause is conjugated for tense/person. In this sentence, that conjugated verb is devas.

In Esperanto, -as marks the present tense.

The dictionary form is devi = to have to / to must (in natural English we would usually say to have to).
When conjugated:

• devas = have to / must
• devis = had to
• devos = will have to

So devas is present tense, but in English the best translation is often simply must.

Yes, nepre is an adverb. In Esperanto, adverbs usually end in -e.

That is why it stays nepre. It does not change for person or number.

Compare:

• bona = good
• bone = well

Here, nepre modifies the idea of the obligation: absolutely / definitely must.

The word order is fairly flexible, but some placements sound more natural than others.

Common possibilities include:

• Vi nepre devas veni.
• Vi devas nepre veni.
• Nepre vi devas veni.

All of these are understandable, but Vi nepre devas veni is a very natural and common order.

Putting nepre earlier can give it more emphasis. Esperanto word order often helps show focus rather than basic grammar.

Yes, if the subject is clear from context, you might hear:

• Nepre devas veni.

But this is less explicit. Esperanto usually allows omitted elements only when the meaning is obvious from the situation.
If you want to be clear and direct, Vi nepre devas veni is better.

Devas usually expresses real necessity, obligation, or strong need. It is often translated as:

• must
• have to
• need to

The exact force depends on context. In this sentence, because of nepre, it sounds especially strong: You absolutely must come.

So yes, here it is very strong.

Its basic meaning is to come, but in context it can overlap with arrive if that is the natural meaning.

For example:

• Li venis hejmen. = He came home.
• In some situations, veni may imply reaching the place, but it is still fundamentally come.

In Vi nepre devas veni, the core idea is simply that the person must come.

A rough pronunciation is:

vee NEH-preh DEH-vas VEH-nee

A few helpful points:

• v is like English v
• e is pronounced like e in bet, but clearer and steadier
• stress in Esperanto normally falls on the second-to-last syllable

So:

• VI
• NE-pre
• DE-vas
• VE-ni

More exactly, the stressed syllables are:

• vi
• NE-pre
• DE-vas
• VE-ni

Esperanto infinitives already show to by their ending -i.

So:

• veni = to come
• fari = to do
• iri = to go

Because veni already means to come, no extra separate word is needed.

It is definitely stronger than should.

• devas = must / have to
• devus = should / ought to

So:

• Vi nepre devas veni. = You absolutely must come.
• Vi nepre devus veni. = You really should come.

That one vowel change matters a lot:

• -as = present/actual
• -us = conditional, often softer or less absolute

Yes, it is quite common. It is often used when someone wants to stress that something is essential or non-optional.

Examples:

• Mi nepre volas iri. = I definitely want to go.
• Vi nepre legu tion. = You absolutely should read that.
• Oni nepre bezonas helpon. = One definitely needs help.

So it is a very useful word to learn early.