Hi JoeArtist, I'm not sure if you want to know the formal expressions or what we usually say. In Indonesia we rarely use the correct Indonesian (bahasa baku/ bahasa Indonesia yang baik dan benar). Even at school or work where it is more formal we mixed the correct Indonesian with slang. These are some Indonesian expressions : Hai/halo = Hi/hello Apa kabar? = How are you? Selamat pagi! = Good morning! Selamat siang! = Good day! Selamat sore! = Good afternoon! Selamat malam! = Good night! Sampai jumpa! = See you! The first two can be used in both formal and colloquial situation as greeting. As for the rest, we don't really use it colloquially. Normally we say "selamat pagi/siang/sore/malam " to a respected person like teacher or on a phone as a greeting e.g. " Selamat siang, bisa bicara dengan Joe?" = Good afternoon, may I speak to Joe? It is sometimes confusing though, when to use selamat pagi/siang/sore/malam. I don't know if there are some definite rule but you can use 'selamat pagi' up to 11am. From 11am - 3pm use 'selamat siang'. From 3pm-6pm use 'selamat sore' and after 6pm 'selamat malam'. Here are some more expressions, these are not formal and often used between friends and family. Makasih (short form of 'terima kasih') = Thanks! Sama-sama = You're welcome/Don't mention it. Mau kemana? = Where are you going? Lagi dimana? = Where are you? Lagi ngapain? = What are you doing now? Commonly used idioms: 'Buaya darat' lit. land crocodile = playboy/ womaniser 'Mati kutu' lit. dead louse = cornered/ don't have a choice 'Kutu buku' lit. dead louse = bookworm 'Cinta monyet' lit. monkey love = puppy love Seperti 'cacing kepanasan' lit. like an overheated worm = not calm/ fidgeting/ panicking or nervous about something 'Kebakaran jenggot' lit. beard on fire = another expression for 'cacing kepanasan' 'Malu-malu kucing' lit. shy cat = want something but shy to admit Well, hope this helps. :)