Exactly.(Riemann) integral is summation with infinitesimal quantities. (It was Leibniz who used long s to denote integration, though. http://jeff560.tripod.com/

Exactly.(Riemann) integral is summation with infinitesimal quantities. (It was Leibniz who used long s to denote integration, though. http://jeff560.tripod.com/calculus.html http://jeff560.tripod.com/calculus.html ) Also, for discrete summation, capital 's'igma is used.