ma is a question word~“ni hao ma”is like that u r asking someone whether he is good or not ~so， we often use it to greet someone who you long time no see~ "ni hao a " is just a greeting,no questions to ask so we use it more in our daily greeting

"Ni hao ma" is not commonly used in common Chinese. In China,we just say hi(hai 嗨) among friends colleague. when your friend introduce you sb,you can say ni hao(你好) i think the (a 啊)is not needed. hehe,jin gong can kao(仅供参考) many people know the hello,even they could't speak english.

"Ni hao ma" it is a polite and formal way to ask someone "How are you doing?" "Ni hao a" is often an everyday language greeting someone.It's an equivalant saying of "Hello" in English.

ni hao ma? = are u all right? ni hao a = hello