, noun 
həˈləʊ 
həˈloʊ plural hellos, hullos, hallos
hello
exclamation (also hullo especially in British English) (British English also hallo) həˈləʊ həˈloʊ 
1 used as a greeting when you meet somebody, when you answer the telephone or when you want to attract somebody's attentionHello John, how are you?Hello, is there anybody there?Say hello to Liz for me.They exchanged hellos (= said hello to each other) and forced smiles.2 (British English) used to show that you are surprised by somethingHello, hello, what's going on here?3 (informal) used to show that you think somebody has said something stupid or is not paying attentionHello? You didn't really mean that, did you?I'm like, ‘Hello! Did you even listen?’ see also golden hello
Usage note: greetingsHello is the most usual word and is used in all situations, including answering the telephone.Hi is more informal and is now very common.How are you? or How are you doing? (very informal) often follow Hello and Hi: ‘Hello, Mark.’ ‘Oh, hi, Kathy! How are you?’Good morning is often used by members of a family or people who work together when they see each other for the first time in the day. It can also be used in formal situations and on the telephone. In informal speech, people may just say Morning.Good afternoon and Good evening are much less common. Good night is not used to greet somebody, but only to say goodbye late in the evening or when you are going to bed.If you are meeting someone for the first time, you can say Pleased to meet you or Nice to meet you (less formal). Some people use How do you do? in formal situations. The correct reply to this is How do you do?