Learn Hardcore Indonesian: Kancing baju saya lepas tadi pagi. - The button of my shirt came off this morning.

Indonesian usually does not use a separate verb like to be (am/is/are/was) in simple statements, and past tense is often shown by context or time words, not verb changes.

In kancing baju saya lepas tadi pagi:

lepas already covers the idea of came off / became loose.
tadi pagi indicates that it happened in the past (earlier today).

So you do not need something like was or came; lepas plus tadi pagi is enough.

Is lepas a verb or an adjective here?

It can be understood in both ways:

As a verb: lepas = to come off / to come undone / to detach
→ The button of my shirt came off this morning.
As an adjective: lepas = off / loose / detached
→ The button of my shirt was off this morning.

Indonesian often does not strictly separate verbs and adjectives the way English does. In this sentence, lepas describes a resulting state (that the button ended up off), but it also implies the event of coming off.

Why is it baju saya and not saya baju for my shirt?

In Indonesian, possessive pronouns usually come after the noun:

baju saya = my shirt
rumah saya = my house
teman saya = my friend

Putting saya before the noun (saya baju) is wrong or would sound like you are trying (and failing) to say something else. The normal pattern is:

[thing] [possessor] → baju saya (my shirt)

Does kancing baju saya mean one button or buttons?

Indonesian nouns usually do not mark singular or plural. So:

kancing baju saya can mean my shirt button (one)
or my shirt buttons (more than one)

Context would clarify it. If you need to be clearer, you can add:

satu kancing baju saya = one button of my shirt
beberapa kancing baju saya = several of my shirt buttons

But in everyday speech, people normally just say kancing baju saya and let context handle the rest.

Could the time expression move? For example, is Tadi pagi kancing baju saya lepas also correct?

Yes. Both are correct and natural:

Kancing baju saya lepas tadi pagi.
Tadi pagi kancing baju saya lepas.

Indonesian time expressions are quite flexible. Putting tadi pagi at the start often adds a little emphasis on when it happened, but the meaning is the same.

What sounds less natural is putting tadi pagi right in the middle like:

?Kancing baju saya tadi pagi lepas.

This is not impossible, but it is less common and can sound a bit awkward. Usually you put time:

at the beginning, or
at the end of the sentence.

What exactly is the nuance of tadi pagi? How is it different from pagi ini?

Both relate to this morning, but with different nuances:

tadi pagi
- literally earlier this morning
- clearly refers to something that is already over / in the past
- Often used even if it is still the same day, but the event is finished.
pagi ini
- literally this morning (today)
- more neutral in time; can feel a bit closer to today’s morning, without strongly emphasizing that it is past.

In your sentence, tadi pagi signals:
The button came off earlier today in the morning, and that’s now in the past.

Could I say pagi tadi instead of tadi pagi?

You can hear pagi tadi, but:

tadi pagi is much more common and neutral.
pagi tadi can sound a bit more marked or literary in some contexts.

For everyday speech, especially as a learner, tadi pagi is the safer and more natural choice.

Is kancing only a noun, or can it be a verb like to button up?

kancing can be both:

Noun – a button
- kancing baju = shirt button
Verb – to button (up) when used as mengancing(i) or with other forms:
- Saya mengancing baju saya. = I buttoned my shirt.
- Tolong kancingkan bajumu. = Please button up your shirt.

In your sentence, kancing is clearly a noun, the subject: the button.

What is the difference between lepas, copot, and terlepas here?

All three can appear in similar sentences but with slightly different flavors:

lepas
- neutral off / detached / free
- Kancing baju saya lepas tadi pagi.
  → My shirt button came off / ended up off this morning.
copot
- very common in speech for things coming off (buttons, wheels, parts)
- often feels a bit more colloquial and action-focused
- Kancing baju saya copot tadi pagi.
  → My shirt button came off this morning. (very natural in casual talk)
terlepas
- ter- often suggests something happened accidentally or as a completed event
- Kancing baju saya terlepas tadi pagi.
  → My shirt button came off / got detached this morning (with a bit of an accidental feel).

All are understandable; copot and lepas are very common in casual contexts.

Is the sentence formal, informal, or neutral?

The sentence:

Kancing baju saya lepas tadi pagi.

is neutral. Reasons:

The pronoun saya is polite/neutral (not very casual like aku, not very formal like certain official styles).
The vocabulary (kancing, baju, lepas, tadi pagi) is ordinary, everyday Indonesian.

You can say this in most situations: to friends, colleagues, even in a polite conversation.

Could I say Kancing bajuku lepas tadi pagi instead of kancing baju saya?

Yes, you can. Differences:

baju saya
- saya is a separate word
- feels neutral/polite, works everywhere
bajuku
- -ku is a suffix meaning my
- often feels a bit more personal or casual
- common in speech, messages, and informal writing

So:

Kancing baju saya lepas tadi pagi.
Kancing bajuku lepas tadi pagi.

Both mean the same thing. Choose saya for safer polite/neutral Indonesian; use -ku when you want a slightly more casual, personal tone.

Why is there no word like sudah to show that the action is completed?

You can add sudah, but it is not required because tadi pagi already clearly puts the event in the past.

Without sudah (fully natural):
- Kancing baju saya lepas tadi pagi.
With sudah (adds a sense of completion/emphasis):
- Kancing baju saya sudah lepas tadi pagi.
  → emphasizes that by that time, the button was already off.

In many everyday situations, Indonesians simply rely on time words like tadi pagi, kemarin, tadi malam, etc., without adding sudah.