Dual and duel are a pair of homophones which means that both the words spell and sound almost similar but their meanings are entirely different from each other. Homophones are usually the cause of confusion among English writers as it is very easy to mix one word for its homophone.
Does the above sentence give you a clear idea of the meanings of dual and duel?
Duel comes from Latin words duellum and bellum that means war, whereas dual come from Latin word duo that means two.
Dual as adjective:
The word dual is used in English language as an adjective where it describes something or someone consisting of two parts, elements, or aspects. Their dual role at work and home make them a better person. In grammar, dual is used in some languages where it denotes an inflection that refers to exactly two people or things (as distinct from singular and plural). The word dual is also used in mathematics where it represents a theorem or expression related to another by the interchange of particular pairs of terms, such as ‘point’ and ‘line’. In aircraft, dual controls are there for the pilot and the co-pilot.
A dual flight landed with a thud.
Dual as noun:
Dual is also used as a noun in English language where it means a dual form of a word as in the dual number. It also means a theorem, expression, etc., that is dual to another.
Dual as verb:
Dual is used as a verb too in English language where it means to convert a road into a dual carriageway.
Though there are no plans to dual the road, a public consultation on the A64 is set to start before the end of the year.
Duel as noun:
Duel (with an e) is used as a noun where it represents a prearranged contest with deadly weapons between two people in order to settle a point of honor. He has seriously wounded men in duels twice. A modern world definition of the noun duel is a contest between two parties.
He won by a short head after a great final-furlong duel.
Duel as verb:
The same meaning of duel is utilized when it is used as a verb in English language that is, to fight a fight or duel.
Shall we duel over this?
But their dual losses on election day—Whitman by 12 percentage points and Fiorina by 9—have raised doubts about their future viability in politics, particularly in California. (LA Times)
Kentucky standout right-handed pitchers Jordan Cooper and Alex Meyer squared off in a pitching duel to complete the UK baseball fall practice season. (UK Athletics)
If that were the case, the Eagles would need to find a dual-threat receiver/returner who could come in and fill the void left by Jackson. (Bleacher Report)
Mr Osborne is a lethally effective political operator. I suspect that today marks the start of an intriguing political duel. (Telegraph)
Lin’s parents were born in Taiwan and retain dual citizenship in Taiwan and the United States. (New York Times)
Dual or duel:
Both words dual and duel originate from Latin but have different root words. They are not related to each other in any way and their similarity in spellings is a total coincidence. Dual are two parts of something and duel is a contest or fight between two parties.