What spelling difference (s) set (s) the English word night and the Greek word seven apart from the same word in other Indo-European languages?

The English language is spoken by 750 million people in the world (I know what you are thinking, that's a LOT of peeps) as either the official language of a nation, a second language, or in a mixture with other languages (such as pidgins and creoles, and many others.) English is the official language in England, Canada, Australia and New Zealand; however, the United States has no official language, because we speak English, Spanish, and a lot of others.