arch·duke 
(ärch-dk, -dyk)
(ärch-dk, -dyk)n.
1. In certain royal families, especially that of imperial Austria, a nobleman having a rank equivalent to that of a sovereign prince.
2. Used as a title for such a nobleman.
[Obsolete French archeduc : arche-, arch- (from Old French; see ARCH-1) + duc, duke (from Old French; see DUKE).]
arch·dukedom n.
- congratulator
- congratulatory
- congregant
- congregate
- congregation
- congregational
- congregationalism
- congregationalist
- congregative
- congregator
- congress
- Congress boot
- congressional
- congressionally
- Congressional Medal of Honor
- congressman
- congressperson
- congresswoman
- Congreve
- congruence
- congruency
- congruent
- congruently
- congruity
- congruous