Roti itu jadi lembik kerana saya terlupa menutup bekasnya.

In Malay, itu after a noun usually means that or functions like the when the thing is already known from context.

So:

• roti = bread
• roti itu = that bread / the bread

Malay normally puts demonstratives after the noun:

• rumah itu = that house
• buku ini = this book

So roti itu is normal Malay word order, even though English would say that bread.

Yes. Here jadi means become.

• jadi = become
• lembik = soft, limp, soggy, no longer firm

So roti itu jadi lembik means the bread became soft/soggy.

In everyday Malay, jadi is very common in speech and writing for become. A more formal alternative is menjadi:

• Roti itu menjadi lembik = The bread became soft

Both are grammatical, but jadi sounds very natural and common in conversation.

Lembik usually means something like:

• soft in a limp way
• not firm
• soggy
• mushy

For bread, lembik suggests it has lost its proper texture, probably because it was left uncovered or not sealed properly. So soft is possible, but in context soggy or limp may give a better feel.

It is often used for things that should be firmer:

• sayur lembik = limp vegetables
• biskut jadi lembik = biscuits become soft/soggy
• badan terasa lembik = the body feels weak/limp

Yes, you can often use sebab instead.

• kerana = because
• sebab = because / reason

In this sentence:

• Roti itu jadi lembik kerana saya terlupa menutup bekasnya.
• Roti itu jadi lembik sebab saya terlupa menutup bekasnya.

Both mean the same thing.

The difference is mostly register:

• kerana = a bit more formal or neutral
• sebab = very common in everyday speech

So if you are speaking casually, sebab is extremely natural.

Terlupa means forgot unintentionally or simply forgot with a sense that it happened without meaning to.

• lupa = forget / forgot
• terlupa = forgot, accidentally failed to remember

In many contexts, lupa and terlupa are close in meaning, but terlupa often sounds a bit more natural when talking about an accidental oversight.

Compare:

• Saya lupa menutup bekasnya. = I forgot to close the container.
• Saya terlupa menutup bekasnya. = I forgot to close the container.
  Slightly stronger sense of an unintended lapse.

So ter- here helps show that it was not deliberate.

Because menutup is the active verb form of tutup when it takes an object.

• tutup = close / shut
• menutup = to close something

Since bekasnya is the object, menutup is very natural:

• menutup bekasnya = to close its container

In careful standard Malay, this is the expected form.

In casual speech, people often shorten it:

• Saya terlupa tutup bekasnya
• Saya terlupa nak tutup bekasnya

These are common in conversation, but terlupa menutup bekasnya is more standard.

Bekas means container, box, or holder, depending on context.

So:

• bekas = container
• bekasnya = its container / the container

The suffix -nya here most naturally refers back to roti itu. So bekasnya means the bread’s container or its container.

This is a very common Malay way to avoid repeating the noun:

• roti itu ... bekasnya = the bread ... its container

In natural English, we would usually say its container or the container it was in.

Yes. In Malay, -nya can do several jobs, and one of them is to make something definite, a bit like the in some contexts.

So bekasnya can be understood as:

• its container
• the container

In this sentence, both lead to the same practical meaning: the speaker forgot to close the container associated with the bread.

This flexibility is very normal in Malay. The exact English translation depends on context more than on the form itself.

Yes, you can reverse it.

The original order is:

• Roti itu jadi lembik kerana saya terlupa menutup bekasnya.

This starts with the result, then gives the reason:

• The bread became soft because I forgot to close its container.

You can also say:

• Kerana saya terlupa menutup bekasnya, roti itu jadi lembik.

That means the same thing. The difference is mainly emphasis:

• main clause first = focuses first on what happened
• reason first = focuses first on why it happened

Both are grammatical.

Yes.

• jadi lembik = became soft
• menjadi lembik = became soft

Menjadi is a fuller, more formal-looking form. In everyday speech, jadi is often preferred because it sounds simpler and more natural.

So these are both fine:

• Roti itu jadi lembik...
• Roti itu menjadi lembik...

If you are aiming for very natural spoken Malay, jadi is excellent here.

Yes, absolutely.

Compare:

• ...saya terlupa menutup bekasnya.
• ...saya terlupa menutup bekas roti itu.

Both are correct.

Difference:

• bekasnya = shorter, smoother, avoids repetition
• bekas roti itu = more explicit, clearer if there could be confusion

Malay often prefers using -nya when the reference is obvious from context.

It is natural and correct, but it leans slightly toward standard or careful Malay because of words like:

• kerana
• terlupa menutup

In everyday conversation, many speakers might say something like:

• Roti tu jadi lembik sebab saya terlupa tutup bekas dia.
• Roti tu jadi lembik sebab saya lupa nak tutup bekasnya.

Features of casual speech there:

• itu → tu
• kerana → sebab
• menutup → tutup
• sometimes bekasnya → bekas dia in speech

So your original sentence is perfectly good Malay, especially in writing or careful speech.

Yes: Malay verbs do not change form for tense the way English verbs do.

In English:

• becomes, became, has become
• forget, forgot

In Malay, the verb itself often stays the same, and time is understood from context:

• jadi can mean become / became
• terlupa already gives the idea of forgot
• no verb ending changes for I, you, he, etc.

So the past meaning in this sentence comes from context, not from verb conjugation. That is a major difference from English and something learners often need to get used to.