Indonesian affixes explained.

Indonesian builds whole vocabularies from a small set of root words plus six affix patterns. Once you can read affixes, you stop translating "new" words — you decode them.

Why this matters more than any other grammar topic

An English speaker who learns 1,000 Indonesian root words doesn't actually have 1,000 words — they have closer to 3,000 once they can recognize affixes. Take the root ajar ("teach"):

• belajar — to learn (ber- + ajar)
• mengajar — to teach (me- + ajar)
• diajar — to be taught (di- + ajar)
• pengajar — teacher / instructor (pe- + ajar)
• pengajaran — teaching, instruction (pe- + ajar + -an)
• pelajaran — lesson (pe- + ajar + -an, with sound shift)
• pelajar — pupil, student (pe- + ajar)

One root, seven words. This pattern repeats across the entire dictionary. Below is what each affix actually does.

ber- (active intransitive verbs)

Adds "to do something" or "to have something" to the root. The action doesn't take an object.

• kerja (work) → bekerja (to work)
• main (play) → bermain (to play)
• sepeda (bicycle) → bersepeda (to ride a bike)
• cerita (story) → bercerita (to tell a story)

Spelling rule: ber- becomes be- before words starting with r (so ber- + renang → berenang, not "berrenang").

me- (active transitive verbs)

The most-used affix. Marks the subject as actively doing something to an object. Comes in five forms depending on the first letter of the root: me-, men-, mem-, meng-, meny-.

• tulis (write) → menulis (to write something) — t drops
• baca (read) → membaca (to read something) — b becomes mb
• ambil (take) → mengambil (to take something) — vowel start gets meng-
• sapu (sweep) → menyapu (to sweep) — s drops, becomes meny-

Don't memorize the rules — just absorb the pairs from your flashcards. Native speakers don't think about it consciously either; the patterns become muscle memory.

di- (passive)

Flips the sentence around: now the object is the subject and the action happens to it. Pair this with me- and you can express almost anything.

• Saya menulis surat. — I write a letter. (active)
• Surat itu ditulis oleh saya. — The letter is written by me. (passive)
• Pintu dibuka. — The door is opened.

Indonesian uses passive constructions far more than English does. When you're describing something happening, think "what verb is being done to it?" rather than "who's doing it?"

ter- (accidental, sudden, or completed)

Three meanings, all related to "without intent" or "in a finished state":

• tidur (sleep) → tertidur (to fall asleep accidentally)
• jatuh (fall) → terjatuh (to fall down suddenly)
• buka (open) → terbuka (open / opened, as a state)
• besar (big) → terbesar (biggest — superlative meaning)

pe- (agent or doer)

Turns a verb into the person or thing that does it.

• main (play) → pemain (player)
• tulis (write) → penulis (writer)
• jual (sell) → penjual (seller)
• ajar (teach) → pengajar (teacher / instructor)

ke-an (state, abstract noun, or unintentional event)

Wraps a root with both ke- and -an. Usually creates an abstract noun ("the state of being X") or describes something happening accidentally.

• baik (good) → kebaikan (goodness, kindness)
• indah (beautiful) → keindahan (beauty)
• hujan (rain) → kehujanan (to get caught in the rain)
• panas (hot) → kepanasan (overheated, suffering from heat)

How to actually learn this

Don't sit down and memorize a table. Instead:

1. Get to ~300 root words first. Affixes only click when you have raw material to apply them to.
2. When you see a new affixed word, look for the root inside it. Speak Indo's flashcards show the root explicitly when one exists.
3. After a month, the patterns become predictive — you'll start guessing meanings of words you've never seen, and you'll be right most of the time.

Practice these patterns in the app

The grammar category covers each affix in detail with examples and quiz questions. The verbs category is where most of the action is — every verb shows its root if it has one.