Rapat itu ditunda sehari.

In Indonesian, itu often means that, and it comes after the noun it modifies.

So:

• rapat = meeting
• rapat itu = that meeting / the meeting

This is normal Indonesian word order. Unlike English, where we say that meeting, Indonesian says meeting that.

In many contexts, itu can also make the noun feel more definite, so rapat itu may be understood as the meeting even if a very literal translation would be that meeting.

Ditunda is a passive form, while menunda is an active form.

• menunda = to postpone, to delay
• ditunda = to be postponed, to be delayed

So:

• Mereka menunda rapat itu. = They postponed the meeting.
• Rapat itu ditunda. = The meeting was postponed.

In your sentence, the meeting is the thing being affected, so Indonesian uses the passive form ditunda very naturally.

Here, di- is a passive verb prefix. It marks that the subject receives the action.

So:

• tunda = postpone / delay
• ditunda = be postponed / be delayed

This di- is different from the separate word di, which means in / at / on as a preposition.

Compare:

• ditunda = was postponed
• di kantor = at the office

A useful clue: the passive prefix di- is written together with the verb, but the preposition di is written separately.

Indonesian often leaves the agent unstated when it is unknown, obvious, or unimportant.

So Rapat itu ditunda sehari focuses on the event itself, not on who did it.

If you want to mention the doer, you can add it:

• Rapat itu ditunda oleh panitia. = The meeting was postponed by the committee.

But in everyday Indonesian, leaving out the agent is very common.

Sehari literally means one day.

It is made from:

• se- = one
• hari = day

So sehari can mean one day as a duration or amount of time.

In this sentence, it usually means the meeting was postponed by one day.

In this sentence, the most natural meaning is usually by one day:

• Rapat itu ditunda sehari. = The meeting was postponed by one day.

However, Indonesian often does not mark this distinction as explicitly as English does. The exact meaning comes from context.

For example:

• if you are talking about rescheduling, sehari will usually mean by one day
• in other contexts, a time expression can sometimes mean for one day

So the sentence can be slightly context-dependent, but postponed by one day is the normal interpretation here.

Because Indonesian often allows a bare time expression after the verb.

So instead of saying something longer, Indonesian can simply say:

• ditunda sehari
• ditunda seminggu
• ditunda dua jam

These mean:

• postponed by/for one day
• postponed by/for a week
• postponed by/for two hours

This compact style is very common and natural.

Yes, you can say satu hari, but sehari is often more natural and compact in this kind of sentence.

Compare:

• ditunda sehari
• ditunda satu hari

Both are understandable. In many cases, sehari sounds smoother because Indonesian often uses se- + unit of time for expressions like:

• sehari = one day
• seminggu = one week
• sebulan = one month
• setahun = one year

Not necessarily. Indonesian verbs do not change form for tense the way English verbs do.

So ditunda by itself does not specifically mean:

• was postponed
• is postponed
• has been postponed
• will be postponed

The time is understood from context, or from extra words such as:

• kemarin = yesterday
• tadi = earlier
• besok = tomorrow
• akan = will
• sudah = already

For example:

• Rapat itu sudah ditunda sehari. = The meeting has already been postponed by one day.
• Rapat itu akan ditunda sehari. = The meeting will be postponed by one day.

Yes, often it could. The root tunda can cover ideas like postpone or delay, depending on context.

In many cases:

• ditunda = postponed
• ditunda = delayed

If the context is a scheduled event like a meeting, postponed is often the best English choice. If the context is more general, delayed may also work.

Because in this sentence, rapat itu is the subject of a passive clause, not the object of an active one.

Compare:

Active:

• Mereka menunda rapat itu.
  • Mereka = subject
  • rapat itu = object

Passive:

• Rapat itu ditunda sehari.
  • rapat itu = subject
  • the agent is omitted

So the sentence is complete as it is.

Yes. An active version would be something like:

• Panitia menunda rapat itu sehari. = The committee postponed the meeting by one day.
• Mereka menunda rapat itu sehari. = They postponed the meeting by one day.

The passive version is very common when the speaker wants to emphasize the meeting rather than the people who postponed it.

By itself, rapat does not show singular or plural. In this sentence, it is normally understood as singular because of context: the meeting or that meeting.

Indonesian often leaves number unmarked unless it needs to be made explicit.

If you really wanted to make it clearly plural, you might say:

• rapat-rapat itu = those meetings

But in ordinary use, context usually tells you whether one or more than one is meant.

Yes, it is very natural.

It is short, clear, and idiomatic:

• rapat itu = the meeting / that meeting
• ditunda = was postponed
• sehari = by one day

This is exactly the kind of compact sentence Indonesian speakers commonly use.