Jangan sampai lupa mengunci jendela malam ini.

Don’t let yourself forget to lock the windows tonight.

Breakdown of Jangan sampai lupa mengunci jendela malam ini.

• lupa: to forget
• jendela: the window
• malam ini: tonight
• jangan sampai: don’t let
• mengunci: to lock

Questions & Answers about Jangan sampai lupa mengunci jendela malam ini.

What nuance does jangan sampai add compared to just jangan lupa?

• Jangan lupa = a simple reminder: don't forget.
• Jangan sampai lupa = stronger/urgent: don't let it happen that you forget; implies there could be a bad consequence if you do.

What does sampai mean in this construction?

Literally it means "until/to," but in jangan sampai + clause/verb it means "don't let it reach the point that …" Examples:

• Jangan sampai terlambat.
• Jangan sampai salah kirim.

Do I need untuk after lupa? Should it be lupa untuk mengunci?

Both are correct:

• Jangan sampai lupa mengunci ... (most common and natural)
• Jangan sampai lupa untuk mengunci ... (a bit more formal or careful)

Why are there two verbs in a row: lupa mengunci?

Indonesian often puts verbs back-to-back without a linker. Verbs like lupa, ingat, ingin, harus, bisa can be followed directly by another verb:

• Saya lupa membawa kunci.
• Dia ingat menutup jendela.

Can I include the subject “you”?

Yes:

• Jangan sampai kamu lupa mengunci jendela malam ini. (informal)
• Jangan sampai Anda lupa ... (polite/formal)
• Jangan sampai kalian lupa ... (plural you) Leaving the subject out is the most typical imperative.

Is mengunci necessary, or can I say kunci?

• Mengunci is the standard verb form.
• In casual speech, the bare root works in imperatives: Jangan lupa kunci jendela.
• Very colloquial pronunciation: ngunci. In writing, prefer mengunci.

Where can malam ini go? Do I need a preposition?

• No preposition is needed: malam ini alone is fine.
• Positions:
  • End (most common): ... mengunci jendela malam ini.
  • Fronted: Malam ini, jangan sampai lupa mengunci jendela.
• Pada malam ini is formal; di malam ini is generally avoided in standard prose.

Is nanti malam different from malam ini?

Both refer to tonight. Nanti malam often implies "later tonight" (commonly used earlier in the day), while malam ini is neutral.

How strong or polite is this sentence? How can I soften it?

It’s a firm reminder, not rude. To soften:

• Add tolong: Tolong jangan sampai lupa ...
• Add final ya: ... malam ini, ya.
• Use state-focus: Pastikan jendelanya terkunci malam ini.
• Add -lah: Janganlah lupa mengunci jendela malam ini.

How do I express “be locked” instead of “lock”?

• Active action: mengunci jendela (to lock the window)
• Resulting state: jendelanya terkunci (the window is locked)
• Passive action: jendela dikunci (oleh ...)

Do I need an article for “the window”? How do I show definiteness or possession?

Indonesian has no articles. Options:

• Contextual definite: jendela
• Explicit definite: jendela itu
• Definite/possessive via -nya: jendelanya = the window / his-her-their window (context decides) For clear possession: jendela rumahmu, jendela kantor itu

How do I say it for multiple windows?

• semua jendela (all the windows)
• Reduplication: jendela-jendela Examples:
• Jangan sampai lupa mengunci semua jendela malam ini.
• Jangan sampai lupa mengunci jendela-jendela malam ini.

Is kelupaan possible here, and what does it add?

Yes: Jangan sampai kelupaan mengunci jendela malam ini.
Kelupaan conveys accidentally/absent-mindedly forgetting; it sounds a bit more colloquial and empathetic.

Why use jangan and not tidak?

• Jangan is the negator for commands/prohibitions.
• Tidak negates statements. Examples:
• Jangan sampai lupa ... (command)
• Saya tidak lupa mengunci ... (statement)