In grammar, this is a part of speech. There are two articles in English: the definite article the and the indefinite article a or an. The definite article identifies a particular noun: the book I need and the indefinite article indicates an unidentified noun: bring me a book. The indefinite article an is used in front of a vowel: an owl.
The George Cross was awarded by King George VI and originally appeared in a small blue canton. The present design dates from 1964 when the islands gained independence. Effective date: 21 September 1964.