Possible cause why my laptop is not charging

My laptop battery stopped charging a week ago. So, it has to be connected to an adapter at all times when it’s on. I looked around and learned that my adapter, battery or motherboard might be the cause of all my troubles. But going by my simple hardware knowledge, the problem cannot be the adapter. Then, someone told me today that the charging system could be the one that’s causing all this. Could anyone please advice which of the three is the most likely cause of my troubles is?
