Määräluku

Määräluku is a Finnish term that translates to "cardinal number" in English. It refers to a type of number that is used to indicate the quantity or size of a set or collection of objects. Cardinal numbers answer the question "how many?" They are the fundamental building blocks of counting and are essential for mathematical operations.

In mathematics, cardinal numbers are a generalization of the concept of natural numbers. While natural numbers typically start from 1 and go on infinitely (1, 2, 3, ...), cardinal numbers encompass the concept of zero and can also represent the size of infinite sets. For finite sets, the cardinal number is simply the number of elements in the set. For example, the set {apple, banana, cherry} has a cardinal number of 3.

The study of cardinal numbers is a significant part of set theory. Georg Cantor developed the theory of infinite cardinal numbers, demonstrating that there are different sizes of infinity. This means that some infinite sets can be put into a one-to-one correspondence with the natural numbers (countable infinity), while others cannot (uncountable infinity).

Cardinal numbers are distinct from ordinal numbers, which indicate position or order within a sequence. While a cardinal number tells us *how many*, an ordinal number tells us *which one* in a sequence. For instance, "three" is a cardinal number, while "third" is an ordinal number.