Kakek adalah seorang pelupa.

Kakek most commonly means grandfather.

A learner should also know that kakek can sometimes be used more generally for an old man or as a respectful way to refer to an elderly male, depending on context. In this sentence, it most naturally means grandfather.

It is also worth noticing that Indonesian does not use capital letters for family words unless they are part of a name or used like a name in direct address.

• Kakek adalah seorang pelupa. = Grandfather is a forgetful person.
• Kakek, sini dulu. = Grandpa, come here first.

So here, kakek is the subject of the sentence.

Adalah is a linking word, similar to to be in English when connecting a subject to a noun phrase.

In Kakek adalah seorang pelupa, it links:

• Kakek = the subject
• seorang pelupa = the description/classification

So the structure is basically:

• Kakek
  • adalah
    • seorang pelupa

However, Indonesian often omits this kind of linking word in everyday speech. So you may also hear:

• Kakek seorang pelupa.
• Kakek pelupa.

These can mean essentially the same thing.

Using adalah makes the sentence sound a bit more formal, explanatory, or written.

Yes. Very often, yes.

Indonesian frequently leaves out the equivalent of is/are when the meaning is already clear. So these are all possible:

• Kakek adalah seorang pelupa.
• Kakek seorang pelupa.
• Kakek pelupa.

They differ slightly in style:

• Kakek adalah seorang pelupa → more formal, complete, slightly more textbook-like
• Kakek seorang pelupa → still fine, a bit less formal
• Kakek pelupa → shorter, very natural in everyday use

So a learner should not assume adalah is always required.

Seorang means one person or, in many contexts, works like a/an before a noun referring to a person.

It is made from:

• se- = one
• orang = person

So:

• seorang guru = a teacher
• seorang dokter = a doctor
• seorang pelupa = a forgetful person

This is not exactly the same as the English article a/an, but it often plays a similar role when talking about a single human being.

Because pelupa can be treated as a noun meaning a forgetful person, and seorang fits naturally before nouns referring to people.

So:

• seorang pelupa = a forgetful person

But Indonesian is flexible, and you can also say:

• Kakek pelupa.

That is also natural and common.

The version with seorang sounds a little more explicit, because it clearly presents pelupa as a person-category:

• He is a forgetful person

Without seorang, it feels more direct:

• He is forgetful

Both are possible, but the nuance is a little different.

This is a very good question, because Indonesian word classes are often more flexible than English ones.

In seorang pelupa, pelupa behaves like a noun:

• a forgetful person

But in sentences like Kakek pelupa, it can feel more adjective-like:

• Grandpa is forgetful

So the simplest way to think about it is:

• pelupa describes someone who tends to forget things
• it can function like a noun or an adjective, depending on the structure

This flexibility is very common in Indonesian.

Lupa and pelupa are related, but they are not used the same way.

• lupa = to forget or forgetful/forgotten depending on context
• pelupa = a forgetful person, someone who habitually forgets things

Examples:

• Saya lupa. = I forgot.
• Dia lupa membawa kunci. = He/She forgot to bring the key.
• Dia pelupa. = He/She is forgetful.

So lupa often describes a particular act or state of forgetting, while pelupa describes a person’s tendency or character.

That is why pelupa is a good choice in this sentence.

The prefix pe- often helps form a noun referring to a person associated with an action, quality, or habit.

Here:

• lupa = forget
• pelupa = a person who forgets easily / a forgetful person

This is not always perfectly predictable for every word, but it is a useful pattern to notice.

Some other examples of pe- formations include words for people connected with an action or role. In pelupa, the idea is basically someone characterized by forgetting.

So if you recognize lupa, it can help you understand pelupa.

Yes, it is correct and understandable, but it sounds a little formal or textbook-like.

In everyday conversation, many speakers would more naturally say:

• Kakek pelupa.

or perhaps:

• Kakek itu pelupa.

The full version with adalah seorang is not wrong at all. It just sounds more like careful written Indonesian or a sentence used for explanation.

So as a learner, it is useful to know both:

• formal / explicit: Kakek adalah seorang pelupa.
• more casual / everyday: Kakek pelupa.

Because Indonesian does not have articles like English a/an/the.

English requires you to choose between:

• a forgetful person
• the forgetful person

Indonesian usually does not mark that in the same way.

Instead, Indonesian uses context, word order, and sometimes words like:

• seorang = a person / one person
• itu = that / the (in some contexts)

So:

• seorang pelupa can feel like a forgetful person
• pelupa itu can mean that/the forgetful person, depending on context

In your sentence, seorang helps give the sense of a because the noun refers to a person.

No. Indonesian does not change verbs or linking words for tense the way English does.

So Kakek adalah seorang pelupa does not contain a special present-tense marker. It is understood as present because of context.

If needed, Indonesian can add time words such as:

• sekarang = now
• dulu = in the past / before
• besok = tomorrow

But very often, no tense marker is used at all.

So the sentence simply states a general fact or description: Grandfather is forgetful.

Yes, absolutely.

Adding itu after kakek makes it more like:

• That grandfather is a forgetful person
• or simply Grandfather is forgetful, with a bit more definiteness depending on context

So these are all possible:

• Kakek pelupa.
• Kakek seorang pelupa.
• Kakek adalah seorang pelupa.
• Kakek itu seorang pelupa.

Adding itu can make the noun feel more specific or more established in the conversation.

No. Seorang is specifically for people.

So it works with human nouns like:

• seorang guru = a teacher
• seorang teman = a friend
• seorang pelupa = a forgetful person

But for things or animals, Indonesian uses other classifiers or simply no classifier, depending on the noun.

That is why seorang is appropriate here: pelupa refers to a person.

Yes. That is a very natural sentence.

• Kakek sangat pelupa. = Grandpa is very forgetful.

This works well because pelupa can function as a descriptive predicate.

Notice that with sangat, you would normally not say:

• Kakek adalah seorang sangat pelupa.

That sounds unnatural.

More natural choices are:

• Kakek sangat pelupa.
• Kakek memang pelupa.
• Kakek seorang yang pelupa. (possible, but less simple)

So if you want to intensify the description, sangat pelupa is the easiest and most natural option.