The lack of an "or" in "petal" may have tipped you off: "petal" isn't related to "portal." All the other words come from the same Latin root: "porta," meaning "passage" or "gate." ("Petal" comes from the Greek "petalon.") "Portal" has been part of the English language for more than 600 years, and in that time it's developed a number of meanings besides the "large door" sense. "Portal" also refers to the entrance to a bridge or tunnel and to a Web site that helps you find other Web sites, among other things.