In our daily lives, these two words are the most common words that we use when talking to or greeting people. They are used more often and are believed to have the same meaning; however, they really do make some questions in minds if they do have differences.
The word hello is defined as an expression or the greeting gesture, express a surprise, or to just answer a telephone call. Normally, hello is used to start a conversation when meeting or have been introduced to a certain person or group of persons. It is also believed that this word as altered from an Old High German word “hate” that is used for hailing the ferryman. The hi on the other hand is also used for greeting gestures, however, it is defined by many as the informal form of the word “hello” or sometimes as an expression for gaining attraction of attention.
It is easy to say that the meaning of hello is more on the formal side of usage such as in formal occasions or meeting and greeting individuals of authority, and hi understood to be on the casual side as it is more commonly used among equals and peers.