Words We Confuse   >>   A vs. An    Examples

A vs. An

• Use A if the next word starts with the sound of a consonant.
• examples:  a toy & a book
• Use A if the first letter of the next word is vowel but the first sound is a consonant.
• when "o" makes the same sound as w in work
• when "e" makes the same sound as the y in yes
• when "eu" makes the same sound as the y in yes
• when "u" makes the same sound as the y in yes
• examples:  a unicorn, a universe, a one man show.

• Use An if the next word starts with the sound of a vowel.
• examples:  an apple, an orange, & an arm
• Use An if the next word starts with a silent 'h', followed by a vowel.
• example:  an hour

Source:   www.A-or-An.com