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.
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 as verb:
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.
Duel as verb:
Shall we duel over this?
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.