Numerosity (sometimes called subitizing) is the most basic of these abilities; it involves quickly determining the quantity of up to about four items or events without counting.

What is a Numerosity?

Legal Definition of numerosity

: the requirement that members of a proposed class formed for a class action be so numerous as to make joinder of the members impracticable.

What is the Denotative of numbers?

1a(1) : a sum of units : total the number of people in the hall.