1. quantities that are infinitely small or approach zero as a limit; in calculus, variables or quantities used in the study of limits and derivatives.
Usage: mathematics; plural form; singular is infinitesimal; foundational concept in calculus and mathematical analysis
2. things or amounts so small as to be negligible or nearly imperceptible.
Usage: figurative or general use

Examples

• In calculus, infinitesimals are used to define the derivative of a function.
• Newton and Leibniz developed calculus using the concept of infinitesimals.
• The difference between the two measurements was infinitesimals.
• Modern analysis has formalized the intuitive notion of infinitesimals.
• Infinitesimals help us understand how functions change at specific points.
• The contribution of each grain of sand to the total weight is infinitesimals.