Learn Hardcore Malay: Saya melihat anak bermain bola di taman. - I see a child playing ball in the park.

Malay has no articles; nouns appear without a, an, the. Definiteness or indefiniteness is understood from context or optionally marked with demonstratives like anak itu (that child) or quantifiers like seorang anak (a child).

What is the function of the prefix ber- in bermain? Why not just use main?

The root main already means play and can act as a verb. Adding ber- forms bermain, highlighting the action as an activity or habit. In everyday speech you might hear both main bola and bermain bola with little difference in meaning.

What tense is melihat, and how do I express present progressive versus simple present?

Malay verbs do not change form for tense. melihat comes from root lihat with active prefix me-, meaning see. Context usually tells you the time. To emphasize ongoing action (present progressive), insert sedang:
Saya sedang melihat anak bermain bola di taman (I am seeing/watching a child playing ball in the park).

Can I move di taman to another position, and does it change the emphasis?

Yes. You can say Saya melihat anak di taman bermain bola. The literal meaning stays the same. Placing di taman immediately after anak emphasizes the child’s location first; keeping it at the end emphasizes the setting of the whole action.

Why is di used in di taman instead of ke?

di marks a static location (at/in/on). ke marks movement toward a location (to). Since the sentence describes where the child is playing, use di taman (in the park). Use ke taman only if you mean going to the park.

Why use saya and can the subject pronoun be dropped? What about aku?

saya is the formal or neutral first-person pronoun. aku is informal. In Malay you can drop the pronoun if context makes it clear:
(Saya) melihat anak bermain bola di taman.
Include saya or aku when you need to clarify who is doing the action or for emphasis.

How do I express past tense or plural in this sentence, for example I saw the children playing ball in the park?

Malay uses time words or context to show tense. To make past: add sudah (already) or telah before the verb: Saya sudah melihat. To pluralize anak, use reduplication: anak-anak. So:
Saya sudah melihat anak-anak bermain bola di taman.
You can also omit sudah if context shows it’s past.

Does melihat take an object directly? Why not say melihat ke anak?

melihat is a transitive verb that takes a direct object, so no preposition is needed. Correct: Saya melihat anak. Incorrect: Saya melihat ke anak. The ke would suggest movement or direction, which you don’t need here.

What’s the difference between anak and anak itu in this sentence?

anak by itself means child in a general or indefinite sense (a child). Adding itu (that) makes it definite (that child). So:

Saya melihat anak bermain bola di taman = I see a child playing ball in the park.
Saya melihat anak itu bermain bola di taman = I see that child playing ball in the park.