Title: Rules which explain the use of definite and indefinite articles

Rule #1 - Specific identity not known

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Use the indefinite article “a” or “an” only with a singular count noun whose specific identity is not known to the reader. Use a before nouns that begin with a consonant sound, and use “an” before nouns that begin with a vowel sound:

Use the article “a” or “an” to indicate any non-specified member of a group or category.

- I think an animal is in the garage
- We are looking for an apartment.

Use the article “a” or “an” to indicate one in number (as opposed to more than one).

- I own a cat and two dogs.

Use the article a before a consonant sound, and use “an” before a vowel sound.

- A boy, an apple

Sometimes an adjective comes between the article and noun.

- An unhappy boy, a red apple

The plural form of “a” or “an” is some. Use some to indicate an unspecified, limited amount (but more than one).

- An apple, some apples

Rule #2 - Specific identity known

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Use the definite article “the” with any noun (whether singular or plural, count or noncount) when the specific identity of the noun is known to the reader, as in the following situations:

Use the article “the” when a particular noun has already been mentioned previously.

- I ate an apple yesterday.
- The apple was juicy and delicious.

Use the article “the” when an adjective, phrase, or clause describing the noun clarifies or restricts its identity.

- The boy sitting next to me raised his hand.
- Thank you for the advice you gave me.

Use the article “the” when the noun refers to something or someone that is unique.

- the theory of relativity
- the 2003 federal budget

Rule #3 - All things or things in general

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Use no article with plural count nouns or any noncount nouns used to mean all or in general.

- Trees are beautiful in the fall. (All trees are beautiful in the fall).
- He was asking for advice. (He was asking for advice in general).
- I do not like coffee. (I do not like all coffee in general).

Additional Information Regarding the Use of Articles
When indicating an unspecified, limited amount of a count or noncount noun, use some.

- I would love some coffee right now (not coffee in general, but a limited amount of coffee).
- It may rain tomorrow. Some rain is good for the crops (a certain amount of rain, as opposed to rain in general).
- There are some drops of water on the table (a limited number, but more than one drop).

Geographical names are confusing because some require the and some do not.
Use the with: united countries, large regions, deserts, peninsulas, oceans, seas, gulfs, canals, rivers, mountain ranges, groups of islands.

- the Gobi Desert
- the United Arab Emirates
- the Sacramento River

Do not use the with: streets, parks, cities, states, counties, most countries, continents, bays, single lakes, single mountains, islands.

- Japan
- Mt. Everest
- San Francisco Bay