[header] How to respond [title] Answer " hello " with a " hello ". [step] If a person says " hey, " they are using a more familiar form of " hello " and you can say " hey " or " hi. " if it's someone you know, such as a friend or colleague, you can say " hey! How are you? " depending on how professional the situation. 
[substeps] If you hear " hiya " this is an english slang greeting that means the same as " hello " or " hey. " you can use " hey " or " how are you? " as potential responses.