Ni vidis strangan rokon.

Vidis is the past-tense form of vidi, which means to see.

In Esperanto, verb endings are very regular:

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

So:

• vidas = see / am seeing
• vidis = saw
• vidos = will see

That makes Ni vidis mean we saw.

They both have -n because they are part of the direct object.

In Esperanto, the direct object usually takes the accusative ending -n.

Here:

• roko = a rock
• rokon = a rock, as the direct object

Since strangan describes rokon, the adjective must match the noun. That means it also takes -n:

• stranga roko = a strange rock
• strangan rokon = a strange rock, as the object

So the sentence literally has:

• Ni = we
• vidis = saw
• strangan rokon = a strange rock

In Esperanto, adjectives agree with the nouns they describe.

That means if the noun is:

• singular or plural
• nominative or accusative

the adjective changes too.

So:

• stranga roko = a strange rock
• strangan rokon = a strange rock (object)
• strangaj rokoj = strange rocks
• strangajn rokojn = strange rocks (objects)

This agreement helps make sentence structure very clear.

Their basic forms are:

• stranga = strange
• roko = rock

Esperanto dictionary forms are usually:

• nouns ending in -o
• adjectives ending in -a
• verbs ending in -i

So in this sentence:

• strangan comes from stranga
• rokon comes from roko

The extra -n is grammatical, not part of the core word.

Esperanto has no indefinite article. In other words, there is no separate word for English a or an.

So:

• roko can mean rock or a rock, depending on context
• stranga roko = a strange rock / strange rock

Esperanto does have a definite article:

• la = the

So:

• strangan rokon = a strange rock
• la strangan rokon = the strange rock

Yes, Esperanto allows more flexible word order than English, partly because the -n ending shows the object clearly.

The normal order here is:

• Ni vidis strangan rokon.

But you could also say:

• Strangan rokon ni vidis.

That still means We saw a strange rock, because rokon has -n, marking it as the object.

Even so, the most neutral and common order is still subject–verb–object, so Ni vidis strangan rokon is the most straightforward version.

Ni is the Esperanto pronoun for we.

Some common pronouns are:

• mi = I
• vi = you
• li = he
• ŝi = she
• ĝi = it
• ni = we
• ili = they

So the sentence starts with the subject ni, meaning the people doing the seeing are we.

Yes, strangan rokon is one noun phrase: a strange rock.

Here:

• rokon is the main noun
• strangan describes that noun

So strangan is simply an adjective modifying rokon. It is not describing the action of seeing.

If you wanted to describe the action instead, you would need a different structure, usually with an adverb:

• Ni strange vidis... would mean something like We saw ... in a strange way, which is different.

A simple pronunciation guide is:

• Ni ≈ nee
• vidis ≈ VEE-dis
• strangan ≈ STRAHN-gan
• rokon ≈ ROH-kon

A few useful pronunciation points:

• Esperanto stress is almost always on the second-to-last syllable
• strangan → STRAN-gan
• rokon → RO-kon
• Each vowel is pronounced clearly:
  • a like ah
  • i like ee
  • o like oh

So the whole sentence is pronounced approximately: NEE VEE-dis STRAHN-gan ROH-kon.

No, not in normal standard Esperanto.

If you said:

• Ni vidis stranga roko

that would be ungrammatical, because vidi takes a direct object, and the direct object should be marked with -n:

• rokon

And since the adjective must agree with the noun, it also needs -n:

• strangan

So the correct form is:

• Ni vidis strangan rokon.

The plural version would be:

• Ni vidis strangajn rokojn. = We saw strange rocks.

Here is what changes:

• stranga → strangaj for plural
• roko → rokoj for plural
• because it is still the direct object, both also take -n
• so:
  • strangaj → strangajn
  • rokoj → rokojn

This shows an important Esperanto pattern:

• -j marks plural
• -n marks accusative
• adjectives match the nouns they describe in both