nonstandard analysis
EnglishEdit
NounEdit
nonstandard analysis (uncountable)
 (analysis) Analysis founded upon the hyperreal number system, i.e., which formally defines and uses infinitesimals, especially differentials.

2010 February 25, Joel David Hamkins, “Answer to "How helpful is nonstandard analysis?"”^{[1]}, mathoverflow.net, retrieved 20121113:
 To be sure, the epsilondelta methods arose in part because mathematicians became unsure of the foundational validity of infinitesimals. But since nonstandard analysis exactly provides the missing legitimacy, the original motivation for adopting epsilondelta arguments appears to fall away.
