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

Приклади використання слова «an»:

She and Ruth were both unarmed, and might beapproaching an unknown danger.
I sufferedinternal injuries to an extent I never cared to investigate.
Where did youever get hold of such an absurd idea?
He made an effort to raise himself, that he might spring atthis man-monster.
I had come suddenly outof very black waters into an unbelievable calm.