Learn Hardcore Indonesian: Teman laki-laki saya mengira saya tidak hadir, ternyata saya duduk di belakang. - My male friend assumed I was absent; it turned out I was sitting in the back.

It means “my male friend.” If you mean “boyfriend,” use pacar (gender-neutral for “boyfriend/girlfriend”) or kekasih (more literary). In casual speech, Indonesians often just say teman saya and let context show the gender, or they might say teman cowok saya (slang) if they really want to emphasize “male friend.”

Can I say Teman saya laki-laki or Teman saya yang laki-laki instead? What’s the difference?

Teman laki-laki saya = a noun phrase: “my male friend” (used as the subject/object).
Teman saya laki-laki = a full clause: “my friend is male,” describing the friend.
Teman saya yang laki-laki = “my friend who is male,” used when you’re distinguishing that friend from others (e.g., among several friends of different genders).

Why is laki-laki hyphenated?

Because it’s a reduplicated form. Standard spelling is laki-laki (with a hyphen). A common single-word synonym is lelaki. Writing “laki laki” (with a space) is nonstandard; “laki²” is texting shorthand only.

What’s the nuance of mengira compared with berpikir, menyangka, saya kira, and kira-kira?

mengira/menyangka: to assume/suppose (often later shown to be wrong or uncertain). Fits well with ternyata (“it turns out…”).
berpikir: to think (the mental process), not necessarily an assumption.
saya kira / kukira: “I think/I suppose.” Can be softer or hedging.
kira-kira: “approximately/about.”
Colloquial: kirain (“I thought…”), nyangka (casual for menyangka).

Do I need bahwa after mengira?

No. It’s optional:

mengira (bahwa) saya tidak hadir — both correct; bahwa sounds a bit more formal.
In colloquial speech, kalau is also used: mengira kalau saya tidak hadir.

Why is it tidak hadir and not bukan hadir?

Use tidak to negate verbs and adjectives; use bukan to negate nouns or pronouns.

hadir functions like a verb/adjective (“to be present”), so you say tidak hadir (“not present/absent”).
You’d use bukan in sentences like Itu bukan teman saya (“That is not my friend”).

Is tidak hadir too formal? What are natural alternatives?

Hadir is somewhat formal. Everyday options include:

nggak/ga datang = didn’t come
nggak/ga hadir = didn’t attend (still okay in speech)
nggak/ga ada = wasn’t there/present
nggak/ga muncul = didn’t show up
absen can mean “absent,” but also “to take attendance” (mengabsen). Use with care.

What does ternyata add to the sentence?

Ternyata signals a revelation or unexpected reality (“it turns out / actually, as it happens”). It contrasts the earlier belief with the discovered fact. Quick contrasts:

sebenarnya: actually/in fact (correcting or clarifying).
rupanya: apparently/seemingly (speaker’s inference).
padahal: even though/whereas (stressing contradiction with what should be the case).
nyatanya: in fact/as a matter of fact (stating reality).

Is the comma before ternyata okay? Could I use a period or semicolon?

Yes. Indonesian allows a comma there as a discourse pause. You can also write:

Teman laki-laki saya mengira saya tidak hadir; ternyata saya duduk di belakang.
Or split it: Teman laki-laki saya mengira saya tidak hadir. Ternyata, saya duduk di belakang. Adding dan is also common: …, dan ternyata …

Why repeat saya? Can I drop it in the second clause?

Repeating saya is clear and natural. You can drop it if context is obvious:

…, ternyata (saya) duduk di belakang. Omitting it relies on the reader to infer the same subject; keep it if there’s any chance of ambiguity.

How do I show past or “was sitting” in Indonesian?

Indonesian doesn’t mark tense on the verb. Context or time words do the job:

Tadi saya duduk di belakang = I was sitting at the back earlier.
Waktu itu saya sedang duduk di belakang = I was in the middle of sitting at the back at that time.
sedang marks an ongoing action at a reference time.

Does di belakang mean “at the back” or “behind (someone/something)”?

Both, depending on context:

“At the back (of the room/bus/class)” when the place is understood.
“Behind [X]”: di belakangnya (behind him/her/it), di belakang gedung (behind the building).
For “the back section,” you can say di bagian belakang. Note: ke belakang means “to the back,” and in some contexts is a polite way to say “to the restroom.”

How do I say “in the very back,” “back row,” or “back seat”?

“In the very back”: paling belakang or bagian paling belakang.
“Back row”: baris/deretan belakang or deretan paling belakang.
“Back seat” (car): kursi/bangku belakang.

Why is it di belakang (two words) and not dibelakang?

Because di here is a preposition meaning “at/in/on,” and prepositions are written separately: di belakang. The attached form di- is a verb prefix (passive voice), e.g., dipakai (“is/was used”). So:

Location: di belakang (separate).
Passive verb: ditulis, dipakai, etc.