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A term coined by Dave Thomas for a kind ofdynamic typing typical of some programming languages, suchas Smalltalk, Ruby or Visual FoxPro, where avariable's run-time value determines the operations thatcan be performed on it.The term comes from the "duck test": if it walks like a duckand quacks like a duck, it must be a duck.Duck typing considers the methods to which a value respondsand the attributes it posesses rather than its relationshipto a type hierarchy. This encourages greater polymorphismbecause types are enforced as late as possible. (http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/100511).