Welcome is a warmer greeting than hello & is usually used for friends or people visiting your home, workplace or country.

I say hi, you say hello... Well, people say "hi", or "hello" as a form of informal greeting, just to make the first verbal contact with someone. Is more like "good evening" or somenthing. On the other hand, "welcome" is said when you want the person (or people) you are talking to feel welcome there, in other words, to feel confortable, at ease, almost at home (usually where you live or where you work).

HEllo= 你好, 哈囉, WELCOME=歡迎

HI=HEllo "HEllo~how are you" And we say "Welcome to ..."