невизначений артикль, уживається перед словами, що починаються з голосного звуку, або німого h (наприкл., an apple, an hour)

Приклади використання слова «an»:

Negoro, always silent, remained for half an hour observing the horizon.
Achmet Zek caught his breath with a muttered exclamation of incredulityand an imprecation.
Mistress Kerr because her father was an enemy of yours.
That night an event which had been long pending was precipitated.
What an enormous one it is, to be sure!