Members.
An 'Empty Set' or a 'Nul Set'.
Strength
That is called the UNION of the two sets.
If all elements of set A are also elements of set B, then set A is a subset of set B.
In this case the room is a set, and the things are the elements of the set. Since the word thing equals o, that is that this room has no elements, is empty, and this room is called an empty set.
Those are called the elements of the set.
A set is a collection of objects called ELEMENTS OR MEMBERS.
A set that contains no elements is called an empty set, often denoted by the symbol ∅ or {}. If a set contains a natural number of elements, it is simply referred to as a finite set. Thus, the classification of the set depends on whether it has zero elements (empty set) or a positive count of natural numbers.
Members outside of a set are called "elements not in the set" or "complementary elements." In set theory, the complement of a set refers to all elements in the universal set that are not part of the specified set. These elements can be denoted using the complement notation, often represented by a prime symbol or a bar over the set.
Empty set or null set
The number of elements in a set is called the "cardinality" of the set. It represents the size or count of distinct elements contained within that set. For example, a set containing three elements has a cardinality of three.
An 'Empty Set' or a 'Nul Set'.
That is called the average or mean.
a set which has no elements in it is called a null set. example - A={}.
This is called the complement of the set.
In mathematics, a finite set is a set that has a finite number of elements. For example, (2,4,6,8,10) is a finite set with five elements. The number of elements of a finite set is a natural number (non-negative integer), and is called the cardinality of the set. A set that is not finite is called infinite. For example, the set of all positive integers is infinite: (1,2,3,4, . . .)
A set that has no elements in common with another set is called a "disjoint set." When two sets are disjoint, their intersection is empty, meaning there are no shared elements between them. For example, the sets {1, 2, 3} and {4, 5, 6} are disjoint sets.