Questions & Answers about Sumpah itu sangat penting.
A natural breakdown is:
- sumpah = oath, vow
- itu = that, the
- sangat = very
- penting = important
So literally it is something like oath that very important, but in natural English it becomes That oath is very important or The oath is very important.
In Indonesian, a present-tense to be verb is often omitted, especially in simple statements where one thing is being described.
So:
- Sumpah itu sangat penting = That oath is very important
- literally, Indonesian just puts the subject and description together
This is very normal. You do not need a separate word for is here.