La radiko estas granda.

In Esperanto, word endings tell you the part of speech:

• -o = noun
  So radiko is a noun: root
• -a = adjective
  So granda is an adjective: big / large

This is one of Esperanto’s most regular features. Once you know the endings, you can often recognize a word’s job in the sentence immediately.

La is the definite article, meaning the.

So:

• la radiko = the root

Unlike English, Esperanto uses only one article: la. There is no separate word for a or an. If there is no article, the noun can often be understood as indefinite, depending on context.

Estas means is / are / am. It is the present-tense form of the verb esti (to be).

In this sentence:

• La radiko estas granda. = The root is big.

It links the subject (la radiko) with the description (granda), just like is in English.

In Esperanto, adjectives can come before or after the noun.

So both of these are possible:

• la granda radiko = the big root
• la radiko estas granda = the root is big

In your sentence, granda comes after estas because it is not directly modifying the noun inside a noun phrase; it is part of the predicate: it tells you what the root is like.

Because granda is an adjective, describing the noun radiko.

• granda = big, large (adjective)
• grande = in a big way, greatly (adverb)

Here, the sentence describes the root, so you need the adjective form:

• La radiko estas granda. = The root is big.

If you used grande, it would not fit the grammar of this sentence.

Actually, it is already matching the noun correctly.

In Esperanto, adjectives agree with the nouns they describe in number and case:

• singular noun → singular adjective
• plural noun → plural adjective
• accusative noun → accusative adjective

Here:

• radiko is singular
• it is not accusative
• so the adjective stays granda

Compare:

• La radiko estas granda. = The root is big.
• La radikoj estas grandaj. = The roots are big.

The -n ending usually marks the direct object in Esperanto.

But in this sentence, there is no direct object:

• La radiko is the subject
• estas granda describes the subject

So no accusative is needed.

That is why you have:

• La radiko estas granda.

and not forms like radikon or grandan.

The subject is la radiko because it is the thing being talked about—the thing that is big.

Structure:

• La radiko = subject
• estas = verb
• granda = predicate adjective

So the sentence pattern is:

• [subject] + [to be] + [description]

This is very similar to English:

• The root
  • is
    • big

Not necessarily. Radiko can mean a literal root, but it can also be used in other contexts.

A very important Esperanto use is in grammar and word-building:

• radiko can mean a word root or stem

So depending on context, La radiko estas granda could refer to:

• a plant root
• a mathematical root
• a linguistic word root

The grammar stays the same either way.

A simple pronunciation guide is:

La ra-DI-ko ES-tas GRAN-da.

A few useful points:

• Stress in Esperanto is usually on the second-to-last syllable
  • ra-DI-ko
  • ES-tas
  • GRAN-da
• The letters are pronounced regularly
• r is typically rolled or tapped
• a is like a in father

So the whole sentence is pronounced in a very regular, predictable way compared with English.

Yes, but it means something slightly different in structure.

• La radiko estas granda. = The root is big.
  This is a complete sentence.
• La granda radiko. = The big root.
  This is just a noun phrase, not a full sentence by itself.

So if you want a full statement, you need estas.

The normal word order is:

• La radiko estas granda.

This is the most natural and straightforward order.

Esperanto word order is fairly flexible, but not completely free in every context. Because the sentence uses esti (to be), the standard order is usually best for learners:

• subject → verb → predicate

So this sentence is a good basic model to remember.