- exceedingly small; minute: Capillaries, the infinitesimal vessels in our circulatory system, are small enough that red blood cells must flow through them single-file.
- Mathematics.
- immeasurably small; less than an assignable quantity:An infinitesimal number is never zero, but it comes pretty close.
- of, relating to, or involving variables having zero as a limit:infinitesimal calculus.
- an infinitesimal quantity.
- a variable having zero as a limit.
- infinitely or immeasurably small
- of, relating to, or involving a small change in the value of a variable that approaches zero as a limit
- an infinitesimal quantity
