Infinitesimal
A
hypothetical number that is larger than zero but smaller than any
positive real
number. Although the existence of such numbers
makes no sense in the real number system, many worthwhile results
can be obtained by overlooking this obstacle.
Note: Sometimes numbers that aren't
really infinitesimals are called infinitesimals anyway. The
word infinitesimal is occasionally used for tiny positive
real numbers that are nearly equal to zero.
See also
Differential, infinity,
infinite
