infinitesimal

nonzero positive ‘number’ smaller than any positive real number, formalizable in a number of ways (surreals, hyperreals etc.)

en-GB/ˌɪnfɪnɪˈtɛsɪml/
en-US/ˌɪnfɪnɪˈtɛsɪməl/

Categories:

superreal numberhyperreal numberdual numbersurreal number