Hello is just a more formal way to say hi. They both mean the same thing.

Hi and hello are practically interchangeable in their usage. They mean the same thing, and are used for the same purpose. However, ‘hello’ is more formal and is appropriately used in formal occasions or in greeting persons of authority. ‘Hi’ as mentioned earlier is more casual and is used among peers and equals. ‘Hello’ is also more appropriate for speeches with a formal setting, like a public address. ‘Hi’ can also be used for speeches however it is not recommended and should only be used when not addressing anybody of official importance, like ambassadors and other public figures. The major difference between these two words is that hello is more formal than hi. Other than that, you are free to use them as you want. In brief: 1. Hello is a word for greeting and is considered appropriately used in formal situations. 2. Hi is also a word for greeting however it is informal or casual. This should not be used in formal settings and should only be used if addressing friends and equals.

"Hello" we say to teachers, and "Hi" to friends and our parents. ( I think so.....) В общем я думаю, что "Hi" мы говорим близким родственникам, родителям, друзьям, коллегам. А вот "Hello" мы говорим не родным и не близким, например: учителям, соседям и т.п.

5 vs 2 letters =)

'Hi' is less formal than 'hello'.