dual: adjective. du·al \ˈdü(-ə)l also ˈdyü-əl\
: having two different parts, uses, etc.
: having two of something
duel: noun. du·el \ˈdü-əl also ˈdyü-\
: a fight between two people that includes the use of weapons (such as guns or swords) and that usually happens while other people watch
Spelling; it matters.