When do you use ㅇ in Korean words/sentences?
It's for some endings because it is -ng.
And it's to use before the other two characters(hangul) to make three in a box, right?
But I get confused sometimes because when I try writing and check the correct answers, there is no need to use ㅇ sometimes, like bulgogi 불고기.

Question

When do you use ㅇ in Korean words/sentences?
It's for some endings because it is -ng.
And it's to use before the other two characters(hangul) to make three in a box, right?
But I get confused sometimes because when I try writing and check the correct answers, there is no need to use ㅇ sometimes, like bulgogi 불고기.

Answer

'ㅇ' has two sound.
first one is '-ng', and second one is 'No sound'
when 'ㅇ' come to first, like '아' '야' '어' 여' '오' 요' '우' 유'....
it has no sound.. 
(it's to use before the other two characters(hangul) to make three in a box, right?_you mentioned this but doesn't need to make three in a box.. just two can be enough)

when 'o' come to bottom of word '방', '강', '송' '핑' etc
it has '-ng' sound

i guess. you might saw  '설악' or '맞아', '같아' etc
in this case 'ㅇ' has also no sound..
 so you write '설악' but read '서락', same way.. 
you write '맞아' but read '마자'

old korean has 'no sound ㅇ' end of word, but now days.. it's not used anymore.. but just ommited.
for example
you can't write "불공깅', if 'ㅇ' in no sound and come to end of word, you must ommit 'ㅇ'.. 
so it should be 불고기

ご自宅で快適に語学を学べるチャンスをお見逃しなく。経験豊富な語学講師陣の中からお選びいただき、今すぐ最初のレッスンにお申し込みください！