Biar has a number of related meanings in both forms of Indonesian. It can mean ‘let,allow’:
Kalo tangan kanan jalan biar aja tangan kiri di belakang.
if hand right move let just hand left at back
If your right hand moves just let your left hand stay behind your back.
Itu enggak mau ikut campur. Itu biar mereka yang ngurusin sendiri.
that not want [get involved] that let them who arrange self
[I] don’t want to get involved in that. Let them take care of it themselves.
It can mean ‘although, even though’:
Aku, biar anak tengah, apa aku minta enggak pernah dikasih tuh.
I although child middle what I request not ever given that
Although I’m the middle child, whatever I ask for is never given.
Tujuh puluh persen cowok-cowok, biar gayanya se-cool-cool as.coolapa, sepreman-preman apa, justru paling sering nangis kalo nonton film.
[70 ] percent males although style-their what as.tough what precisely most often cry if watch movie
Seventy percent of males, although they act as cool as anything, as tough as anything, are precisely the ones who most often cry when they go to the movies.
It can also mean ‘so that, in order that’. In Formal Indonesian biar does not occur with this meaning; supaya is the most frequent word in this meaning while agar is also common in formal writing. However, in Colloquial Jakartan Indonesian biar is the common word:
Gue harus meniti karir biar gue sukses.
I must pursue career so.that I succeed
I have to pursue my career so that I’m successful.
Ini gua tutup mata yah, biar gua bisa imagine.
this I close eye dp so.that I can imagine.
I’ll close my eyes, alright, so that I can imagine it.
A: Tiba-tiba kenapa suara elu jadi ngebas gitu, Fer?
A: suddenly why voice your become bass like.that F
A: Why has your voice suddenly gone bass like that, Fer?
B: Biar seksi.
B: so.that sexy
B: So that it’s sexy.
CJI Colloquial Jakartan Indonesian
dp discourse particle
FI Formal Indonesian
H High style; forms associated with FI
L Low style; forms associated with CJI
Reference: Colloquial Jakartan Indonesian (Pacific Linguistics, 581) by James Neil Sneddon (2006)