Learn Hardcore Indonesian: Dia lupa memakai helm kemarin, hampir saja terjadi kecelakaan. - She/He forgot to wear a helmet yesterday; an accident almost happened.

In Indonesian, time expressions like kemarin, besok (tomorrow), tadi (earlier), nanti (later) are quite flexible in position. With this sentence you can say:

Dia lupa memakai helm kemarin.
Kemarin dia lupa memakai helm.
Dia kemarin lupa memakai helm. (more colloquial, but acceptable)

All three are understandable and natural.
Putting kemarin at the end, as in the original sentence, is very common in everyday speech and slightly emphasizes when it happened, after giving the main information.

Why is there no subject in hampir saja terjadi kecelakaan? Who is doing the action?

In Indonesian, when you talk about events that happen, you often don’t mention a subject like “it” or “there” (as English does in “there was almost an accident”).

Terjadi kecelakaan literally: happened an accident
→ More natural English: an accident happened or there was an accident.

So:

hampir saja terjadi kecelakaan
= an accident almost happened / there was almost an accident.

The sentence doesn’t need a subject like it or there. Indonesian simply uses the verb terjadi (to happen) directly with the noun kecelakaan (accident). This impersonal style is very common.

What is the nuance of hampir saja? How is it different from just hampir?

Both hampir and hampir saja mean almost, but hampir saja often feels a bit more dramatic or emphatic.

hampir terjadi kecelakaan
= almost happened an accident → there was almost an accident
hampir saja terjadi kecelakaan
= there was almost an accident, with a stronger feeling of “That was close!”

Saja here doesn’t add meaning you can easily translate word‑for‑word; it softens/emphasizes the expression, giving it a more emotional or conversational tone. You’ll see similar patterns:

Dia hampir jatuh. – He almost fell.
Dia hampir saja jatuh. – He nearly fell / He almost fell (wow, close call).

Both are correct; hampir saja is very natural in spoken Indonesian when talking about near-misses or close calls.

What does lupa do in this sentence? Is it like a verb, and does it need memakai after it?

Lupa is a verb/adjective meaning to forget or forgot / forgetful, depending on context. Here it works like the verb to forget:

Dia lupa memakai helm.
= He/She forgot to wear a helmet.

In this pattern, lupa is followed by another verb, like English “forget to …”:

lupa memakai helm – forgot to wear a helmet
lupa membawa dompet – forgot to bring a wallet
lupa mengunci pintu – forgot to lock the door

So yes, here lupa naturally takes a verb after it, and memakai is that verb.

What is the difference between memakai and pakai? Could I say Dia lupa pakai helm?

Yes, you can say Dia lupa pakai helm, and it’s very common in everyday speech.

The difference:

memakai – more complete, slightly more formal; common in writing and neutral speech.
pakai – shorter, more colloquial; very common in spoken Indonesian.

Meaning-wise, there’s no real difference here:

Dia lupa memakai helm kemarin.
Dia lupa pakai helm kemarin.

Both mean He/She forgot to wear a helmet yesterday.

Using pakai instead of memakai is one of the most common informal simplifications.

Why is it memakai helm, not memakai sebuah helm? Where is “a” or “the”?

Indonesian normally doesn’t use articles like a / an / the. The noun helm by itself can be:

a helmet
the helmet
helmets (plural), depending on context.

So:

Dia lupa memakai helm.
can mean He/She forgot to wear a helmet.

You can add a word to clarify, but it’s not needed in this simple context:

Dia lupa memakai sebuah helm. – grammatically possible, but sounds a bit stiff/unusual here.
Dia lupa memakai helmnya. – He/She forgot to wear his/her helmet (referring to a specific helmet).

In everyday Indonesian, you usually just say memakai helm. The listener fills in a/the automatically.

What does terjadi mean exactly, and why use it instead of ada?

Terjadi means to happen / to occur.

terjadi kecelakaan – an accident happened / there was an accident
terjadi gempa – an earthquake happened / there was an earthquake

Using terjadi emphasizes the event itself.

You might think of ada (to exist / there is/are), but:

hampir ada kecelakaan is understandable, but sounds less natural and less idiomatic.
hampir saja terjadi kecelakaan is the standard, natural way to say there was almost an accident.

For events (accidents, disasters, incidents), terjadi is the usual verb.

Does dia mean “he” or “she”? How do you know which one?

Dia is a gender-neutral third-person singular pronoun. It can mean:

he
she

Indonesian pronouns usually don’t show gender. You only know from context:

Dia lupa memakai helm kemarin…
could be He forgot to wear a helmet yesterday…
or She forgot to wear a helmet yesterday…

If you really need to specify gender, you’d usually add more information or use the person’s name, not change the pronoun.

How do we know this sentence is in the past? There is no tense marking like “forgot” vs “forget”.

Indonesian verbs don’t change form for tense. Lupa can mean forget or forgot, depending on context.

Time is normally shown by:

Time words like kemarin (yesterday), tadi (earlier), besok (tomorrow), nanti (later), etc.
Context, previous sentences, or a narrative frame.

Here, kemarin (yesterday) clearly puts the sentence in the past:

Dia lupa memakai helm kemarin.
= He/She forgot to wear a helmet yesterday.

If you remove kemarin, Dia lupa memakai helm could be interpreted as either He/She forgot to wear a helmet (past) or He/She tends to forget to wear a helmet (general), depending on the wider context.

Can I change the word order, like Kemarin dia lupa memakai helm or Dia kemarin lupa memakai helm? Do they sound natural?

Yes, both are natural. Word order with time expressions is flexible:

Dia lupa memakai helm kemarin.
Kemarin dia lupa memakai helm.
Dia kemarin lupa memakai helm.

All are acceptable, with only slight differences in emphasis:

Starting with Kemarin (2) puts a little more focus on yesterday.
Dia kemarin lupa… (3) is common in speech and casual writing; it feels a bit more conversational.

There’s no big change in meaning; they all describe the same past event.

Is kecelakaan singular or plural here? Could it mean “accidents”?

Kecelakaan by itself is usually understood as an accident or the accident, depending on context. Indonesian does not mark plural on the noun by default.

terjadi kecelakaan → an accident happened / there was an accident
terjadi kecelakaan-kecelakaan or banyak kecelakaan → accidents happened / many accidents

In hampir saja terjadi kecelakaan, we normally interpret it as there was almost an accident (one event), because we’re talking about a single near-miss connected to one person forgetting a helmet. Context guides the singular/plural reading.