Learn Hardcore Indonesian: Saya membeli kacamata baru karena mata saya lelah. - I bought new glasses because my eyes are tired.

In Indonesian, descriptive adjectives typically follow the noun (noun + adjective). So kacamata baru literally means glasses new. Placing baru before the noun would change its function (see the next question).

Does baru mean “new” or “just”? How would I say “I just bought new glasses”?

Both, depending on position:

After a noun, baru = new: kacamata baru (new glasses).
Before a verb phrase, baru = just/recently: Saya baru membeli (I just bought). To say “I just bought new glasses”: Saya baru membeli kacamata baru (two different senses of baru; perfectly natural).

Why membeli and not beli? What’s the difference?

membeli = formal/neutral, with the prefix meN- attached to the root beli (buy). Here, meN- + beli → membeli.
beli (without the prefix) is very common in casual speech: Saya beli kacamata baru sounds perfectly natural in conversation.

How do I show past tense? Does membeli mean “bought” specifically?

Verbs in Indonesian don’t change for tense. Context or time words show time:

Past/completed: sudah, telah (formal), tadi, kemarin, barusan.
- Saya sudah membeli kacamata baru.
- Tadi saya membeli kacamata baru.

Is kacamata singular or plural? Do I need a measure word?

Kacamata (eyeglasses) is treated as a single item. You can say:

(one) sebuah kacamata or simply kacamata.
“a pair of glasses” can be sepasang kacamata, but sebuah kacamata is more common. For plurals, Indonesian usually leaves the noun unchanged: beberapa kacamata (several pairs of glasses).

Can I start the sentence with karena? What about commas?

Yes. If the because-clause comes first, use a comma:

Karena mata saya lelah, saya membeli kacamata baru. If it comes after, a comma is usually unnecessary:
Saya membeli kacamata baru karena mata saya lelah.

What’s the difference between karena, sebab, gara-gara, and lantaran?

karena: neutral, most common.
sebab: more formal/literary; synonymous with karena.
gara-gara: colloquial and often implies a negative/annoying cause (because of).
lantaran: formal/literary alternative to karena.

Do I need adalah in mata saya lelah?

No. Adjectives can be predicates in Indonesian. Mata saya lelah is correct and natural. Mata saya adalah lelah is ungrammatical; adalah is used before a noun phrase, not an adjective.

Should I repeat saya in mata saya? Could I say karena mata lelah?

Including the possessor makes it clear: karena mata saya lelah (because my eyes are tired). Karena mata lelah is grammatically fine but could sound generic or ambiguous. You can also use the enclitic: karena mataku lelah (informal).

What’s the difference between saya, aku, gue, and the possessive -ku?

saya: neutral/polite; widely safe.
aku: informal, friendly.
gue: very casual (Jakarta slang). Possessives:
mata saya (neutral/polite),
mataku (informal; -ku attaches without a space),
mata gue (very casual),
mata Anda (formal, using Anda).

Is there any nuance difference among lelah, capek/capai, and letih?

lelah: neutral/standard, slightly formal; good in writing and polite speech.
capek/capai: very common colloquial; you’ll hear capek a lot.
letih: formal/poetic. Stronger forms: sangat lelah, kelelahan (exhausted, over-fatigued).

Can I say kacamata yang baru instead of kacamata baru?

Yes, but yang adds specificity/contrast or turns the adjective into a clearer modifier. Use kacamata yang baru when referring to a particular one already known or to contrast with an old one. For a simple description, kacamata baru is default.

How do I clearly say “both my eyes”?

Use kedua:

Kedua mata saya lelah (both my eyes are tired). Avoid mata-mata for pluralization; mata-mata means spies.

Any pronunciation tips for this sentence?

c is pronounced like English ch: kacamata → ka-cha-ma-ta.
The e in membeli and lelah is the schwa sound (like the a in about).
h at the end of lelah is pronounced lightly. Indonesian stress is relatively even; don’t over-stress syllables.

What’s the difference between membeli and membelikan?

membeli [objek]: buy something.
membelikan [orang] [objek]: buy something for someone (benefactive). Example: Saya membelikan ayah kacamata baru (I bought Dad new glasses).

Could I use untuk instead of karena here?

No. karena gives a cause (because), while untuk gives a purpose (for/to).

Cause: Saya membeli kacamata baru karena mata saya lelah.
Purpose: Saya membeli kacamata baru untuk mengistirahatkan mata. (I bought new glasses to rest my eyes.)

Is kacamata one word or two (kaca mata)?

Modern standard spelling is one word: kacamata (per KBBI). You may still see kaca mata in older texts, but kacamata is preferred today.