A scalar implicature is a quantity implicature based on the use of an informationally weak term in an implicational scale.
The use implicates that all similar utterances using an informationally stronger term are not true because, according to the conversational maxim of quantity, a speaker would ordinarily be required to make a stronger, more informative utterance if a true one were available.
Levinson, Stephen C. 1983.Pragmatics. Cambridge, England: Cambridge University.
Gazdar, Gerald. 1979.Pragmatics: Implicature, presupposition, and logical form. New York: Academic.