indefinitely or exceedingly small; minute

infinitesimal vessels in the circulatory system.

immeasurably small; less than an assignable quantity

to an infinitesimal degree.

of, pertaining to, or involving infinitesimals.

an infinitesimal quantity.

Mathematics . a variable having zero as a limit.

adjective

big , huge , large , significant , substantial

adjective

atomic , imperceptible , inappreciable , inconsiderable , insignificant , little , microscopic , miniature , minuscule , minute , negligible , teeny * , tiny , unnoticeable , small