English Grammar

Articles

a = indefinite article (not a specific object, one of a number of the same objects) with 

We use a

1. When a noun begins with a consonants.

• a basket
• a cat
• a dog
• a girl
• a pumpkin

2.  When a noun begins with a vowel sound or sounded like a consonant.

• a uniform
• a one-way street
• a European
• a unit

an = indefinite article (not a specific object, one of a number of the same objects) with vowels 

We use an

1. when the noun begins with a vowel sound (a,e,i,o,u).

• an aeroplane
• an eagle
• an island
• an organ
• an umbrella

2. when then noun begins with a silent 'h'.

• an honour
• an hour
• an honest boy

Remember, using a or an depends on the sound that begins the next word. So...

• a + singular noun beginning with a consonant: a boy; a car; a bike; a zoo; a dog
• an + singular noun beginning with a vowel: an elephant; an egg; an apple; an idiot;an orphan
• a + singular noun beginning with a consonant sound: a user (sounds like 'yoo-zer,' i.e. begins with a consonant 'y' sound, so 'a' is used); a university; a unicycle
• an + nouns starting with silent "h": an hour
• a + nouns starting with a pronounced "h": a horse 
• In some cases where "h" is pronounced, such as "historical," you can use an. However, a is more commonly used and preferred. e.g. A historical event is worth recording.

If the noun is modified by an adjective, the choice between a and an depends on the initial sound of the adjective that immediately follows the article:

• a broken egg
• an unusual problem
• a European country (sounds like 'yer-o-pi-an,' i.e. begins with consonant 'y' sound)

Remember, too, that in English, the indefinite articles are used to indicate membership in a group:

• I am a teacher. (I am a member of a large group known as teachers.)
• Brian is an Irishman. (Brian is a member of the people known as Irish.)
• Seiko is a practicing Buddhist. (Seiko is a member of the group of people known as Buddhists.)