From Longman Dictionary of Contemporary Englishinfinitesimalin‧fin‧i‧tes‧i‧mal /ˌɪnfɪnəˈtesəməl◂/ adjective SMALLextremely small SYN minuscule infinitesimal changes in temperature —infinitesimally adverb infinitesimally small
Examples from the Corpus
infinitesimal• The risk of getting AIDS from a health-care worker is infinitesimal.• Even an infinitesimal change in temperature will be recorded by the equipment.Origin infinitesimal (1600-1700) Modern Latin infinitesimus “infinite in rank”, from Latin infinitus 