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Order of a group
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This article defines an arithmetic function on groups
Definition
QUICK PHRASES: size of a group, cardinality of a group, size of the underlying set, number of elements
Symbol-free definition
The order of a group is the cardinality of its underlying set.
Definition with symbols
The order of a group G is the cardinality of G as a set. it is denoted as 
.
Facts
Subgroup
By Lagrange's theorem, the order of any subgroup divides the order of the group.
The converse is not always true, that is, there may exist numbers dividing the order of the group with no subgroups of those orders.
In particular, this also means that the order of an element in the group divides the order of the group. Hence, the exponent of a group divides its order.
Quotient
The order of any quotient of a group also divides the order of the group.
Computation
Template:GAP command for function
The GAP command to compute the order of a group is:
Order (group);where
groupmay either be an on-the-spot definition of a group or a name for something defined earlier.
References
Textbook references
- Algebra by Michael Artin, ISBN 0130047635, 13-digit ISBN 978-0130047632, More info, Page 47, Point (2.10)
