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Order (group theory)

From Online Dictionary of Crystallography

Revision as of 11:11, 5 June 2014 by MassimoNespolo (talk | contribs) (languages (Ja))

Ordre (Fr); Ordnung (Ge); Orden (Sp); Ordine (It); 位数 (Ja).


If G is a group consisting of a finite number of elements, this number of elements is the order of G. For example, the point group m3m has order 48.

For an element g of a (not necessarily finite) group G, the order of g is the smallest integer n such that gn is the identity element of G. If no such integer exists, g is of infinite order. For example, the rotoinversion 3 has order 6 and a translation has infinite order. An element of order 2 is called an involution.