(geometry) the interchangeability of the roles of points and planes in the theorems of projective geometry (physics) the property of matter and electromagnetic radiation that is characterized by the fact that some properties can be explained best by wave theory and others by particle theory
A duality is a situation in which two opposite ideas or feelings exist at the same time
the concept that electrons (and all particles) behave both as classical particles and as waves depending on how they are observed (so never both at the same time)
is the very foundation of double entry book keeping system and it comes from the fact that every transaction has a double (or dual) effect on the position of a business as recorded in the accounts For example, when an asset is bought, another asset cash (or bank) is also and simultaneously decreased OR a liability such as creditors is also and simultaneously increased
(physics) the property of matter and electromagnetic radiation that is characterized by the fact that some properties can be explained best by wave theory and others by particle theory
The issuance of credit cards from both major bank card associations (Visa and MasterCard) by an individual bank