Learn Hardcore Indonesian: Kata itu mudah dimengerti.

In Indonesian, demonstratives like ini (this) and itu (that) usually come after the noun when they behave like determiners, similar to this/that in English:

kata ini = this word
kata itu = that word

When ini/itu comes before a word, it often behaves more like a pronoun (this/that one) followed by extra information, not a simple noun phrase:

itu kata yang saya maksud = that is the word I mean

So:

kata itu = that word (normal, most common)
itu kata... = that is the word... (usually needs more after it)

What is the difference between itu and ini here?

Both are demonstratives, but:

ini = this (near the speaker, or just mentioned and now focused)
itu = that (farther away, or already known/mentioned, or more general)

So:

Kata ini mudah dimengerti. = This word (the one I’m focusing on right now) is easy to understand.
Kata itu mudah dimengerti. = That word (the one previously mentioned / that you already know / we’re referring to) is easy to understand.

In many contexts, itu can also feel a bit more neutral, not strongly “far away”.

What does mudah mean, and what part of speech is it?

Mudah means easy.

It is an adjective. In this sentence it describes how the word is:

mudah dimengerti ≈ easy to understand

Indonesian adjectives normally come after the noun (kata mudah = easy word), but here the whole phrase mudah dimengerti functions as the predicate, not as a modifier before the noun.

Why is it dimengerti and not mengerti?

Mengerti means to understand (active voice).
Dimengerti is the passive form: to be understood.

Indonesian often uses the passive when English uses an adjective + infinitive pattern:

Kata itu mudah dimengerti.
Literally: That word is easy to be understood.
Natural English: That word is easy to understand.

So you don’t say:

✗ Kata itu mudah mengerti. (this sounds wrong)

because mudah normally describes how easy it is to be understood, not how easy it is to understand others.

How is dimengerti formed, and what is its root word?

The root is erti (from Malay/Indonesian root related to “meaning, sense”).

Active form:

mengerti = to understand
- meN- (active prefix) + erti

Passive form:

dimengerti = to be understood
- di- (passive prefix) + mengerti

So structurally:

erti → mengerti (active) → dimengerti (passive)

Where is the person who does the understanding? Why is there no by me / by us in the sentence?

Indonesian often uses agentless passive constructions. The doer of the action is simply not mentioned if it’s obvious, general, or unimportant.

Kata itu mudah dimengerti.
= The word is easily understood (by people in general / by listeners / by readers).

If you want to specify the agent, you can add oleh + agent:

Kata itu mudah dimengerti oleh anak-anak.
= That word is easy to understand for/by children.

But in many cases, just leaving out the agent sounds the most natural.

Is mudah dimengerti functioning more like a verb or an adjective phrase?

Grammatically, it’s a predicate phrase that combines:

mudah (adjective) = easy
dimengerti (passive verb) = to be understood

Together they work similarly to an adjectival predicate:

Kata itu → subject
mudah dimengerti → what is being said about the subject

In English terms, think of it like:

That word is easily understood / is easy to understand.

So it behaves more like an adjectival description than a simple action verb.

Can I also say Kata itu gampang dimengerti? What is the difference between mudah and gampang?

Yes, you can say:

Kata itu gampang dimengerti.

Differences:

mudah
- Neutral, standard, used in formal and informal contexts.
gampang
- More informal/colloquial, common in everyday speech.

Meaning-wise, both mean easy, so:

mudah dimengerti ≈ gampang dimengerti
with a slight register difference (formality level).

Is mudah untuk dimengerti also correct? What is the nuance compared to mudah dimengerti?

Both are acceptable:

Kata itu mudah dimengerti.
Kata itu mudah untuk dimengerti.

Nuance:

Sentence 1 (without untuk) is the most natural and common.
Sentence 2 (with untuk) can sound a bit more explicit or careful, but sometimes a bit wordier.

In many cases, Indonesian omits untuk where English might use to or in order to. So mudah dimengerti is usually preferred.

How would I say Those words are easy to understand instead of That word is easy to understand?

You need to make kata plural:

Kata-kata itu mudah dimengerti.
= Those words are easy to understand.

Notes:

Reduplication (kata-kata) is a common way to mark plural nouns in Indonesian.
Often, the plural meaning is also clear from context, so you might just see kata itu used generically for “the words,” but kata-kata itu is the clearest explicitly plural form.

Can I drop itu and just say Kata mudah dimengerti?

You can, but the meaning changes and it becomes ambiguous or odd:

Kata itu mudah dimengerti.
= That word is easy to understand.
Kata mudah dimengerti.
- Could be interpreted as The word mudah is understood,
- or just sound incomplete / unclear, because now kata looks like a generic noun (word) without a determiner.

If you want to talk about words in general, you might say:

Kata-kata dalam buku ini mudah dimengerti.
= The words in this book are easy to understand.

So for that specific word, keep itu: Kata itu mudah dimengerti.

Is this sentence formal, informal, or neutral in style?

Kata itu mudah dimengerti. is neutral in style:

Suitable for spoken and written Indonesian.
Fine in conversations, classrooms, and also in written comments like:
- Penjelasannya singkat dan kata-katanya mudah dimengerti.
  (The explanation is brief and the words are easy to understand.)

If you wanted it more casual, you might choose gampang:

Kata itu gampang dimengerti. (more informal)

For more formal, you might use a synonym like dipahami:

Kata itu mudah dipahami. (a bit more formal/academic-sounding)